Mastering The Windows XP Registry

The Recovery Console
The Windows XP Recovery Console is a tool that allows recovery from a number of failures. Previously, all you could do was boot another copy of Windows XP and hack your way around, replacing files, even registry components, in the blind hope that you would somehow fix the problem.
With Windows XP, you have two tools to use: the Recovery Console and the Safe Mode feature.
The Recovery Console is a powerful, simple (no, that's not an oxymoron!) feature that is supplied with Windows XP, but it is not installed by default. The Windows XP Safe Mode works in the same manner as the Safe Mode found in other versions of Windows. You can modify a number of system settings using Safe Mode (such as video modes). Installing the Recovery Console after the system has failed is quite like locking the barn door
after the horse has been stolen—it really won't work that well.
Installing the Recovery Console
The Recovery Console must be installed before disaster strikes. It will be difficult (maybe even impossible) to install it after a disaster has reared its ugly head. So, let's install the Recovery Console right now.
First, you must use the Windows XP distribution CD (or share containing the appropriate files, if installing from a network device). The Recovery Console is installed using the winnt32.exe program. The winnt32.exe program is the same program that is used to install Windows XP; however, by selecting the correct option, you are able to tell winnt32.exe to not install Windows XP, but to install the Recovery Console instead.
Note It is not possible to install the Recovery Console at the same time as Windows XP. You must first install Windows XP, then install the Recovery Console. If you have multiple copies of Windows XP installed, it is only necessary to install the Recovery Console one time—the Recovery Console will work with as many copies of Windows XP as are
installed.

Follow these steps to install the Recovery Console from the Windows XP distribution CD:
1. Insert the distribution CD and change into the i386 directory.
2. Run winnt32.exe using the /cmdcons option. Typically, no other options are needed, though some users may wish to specify source options, especially if installing from a network share rather than a hard drive.
3. The installation program contacts Microsoft to check for updates to this Windows XP component.

What's in the Recovery Console?
The Recovery Console consists of a minor modification to the boot.ini file, and the addition of a hidden directory on the boot drive. The added directory's name is cmdcons. The change to the boot.ini file is simply the addition of another line providing for a new boot option:
C:\cmdcons\bootsect.dat="Microsoft Windows Recovery console" /cmdcons
This option consists of a fully qualified file name (C:\cmdcons\bootsect.dat), a text description (Microsoft Windows Recovery Console), and a boot option (/cmdcons).
As everyone should be well aware, the Windows XP Boot Manager is able to boot virtually any operating system (assuming that the operating system is compatible with the currently installed file system).

How Windows XP Supports Booting other Operating Systems
Windows XP can be told to "boot" any directory or file location. For example, the Recovery Console is saved in the cmdcons directory. In the cmdcons directory is a 512-byte file named bootsect.dat. Windows XP will treat a file named bootsect.dat exactly as if it were a hard disk's boot sector. In fact, one could, theoretically, copy the bootsect.dat file to a drive's boot sector location and cause that operating system to be booted directly.

One use for this technology is in a multiple-boot configuration where the other operating system or systems are not compatible with Windows NT (such as Windows 95/98/Me).
The Recovery Console does qualify as an operating system, though it is very simple—and limited.
A major question will always be this: is the Recovery Console secure? In most situations, the
Recovery Console is actually quite secure. The user, at startup of the Recovery Console, is prompted for two pieces of information:
• Which Windows XP installation is to be repaired (assuming that there is more than one Windows XP installation!).
• The Administrator's password for that installation. The Recovery Console then uses the installation's SAM to validate this password to ensure the user has the necessary permission to use the system.
A situation comes to mind: if the Administrator's password is lost or otherwise compromised, not only may it be impossible to use the Recovery Console, but anyone with access to the compromised password could modify the system with the Recovery Console. This is not really an issue, though. If the Administrator's password is lost, that's life. It will be difficult, if not impossible, to recover the password. If the security of the Administrator's password is compromised, then it will be necessary to repair the damage—changing the password is mandatory in this case. In either case, the Recovery Console is no less secure than Windows XP is.
The cmdcons directory holds over 100 files.

Registry Disassembled tutorial

The registry is a hierarchical database that contains virtually all information about your computer's configuration. Under previous version of Windows, those setting where contained in files like config.sys, autoexec.bat, win.ini, system.ini, control.ini and so on. From this you can understand how important the registry is. The structure of the registry is similar to the ini files structure, but it goes beyond the concept of ini files because it offers a hierarchical structure, similar to the folders and files on hard disk. In fact the procedure to get to the elements of the registry is similar to the way to get to folders and files.
In this section I would be examing the Win95\98 registry only although NT is quite similar.
The Registry Editor
The Registry Editor is a utility by the filename regedit.exe that allows you to see, search, modify and save the registry database of Windows. The Registry Editor doesn't validate the values you are writing: it allows any operation. So you have to pay close attention, because no error message will be shown if you make a wrong operation.
To launch the Registry Editor simply run RegEdit.exe ( under WinNT run RegEdt32.exe with administer privileges).
The registry editor is divided into two sectios in the left one there is a hierarchical structure of the database (the screen looks like Windows Explorer) in the right one there are the values.
The registry is organized into keys and subkeys. Each key contains a value entry , each one has a name, a type or a class and the value itself. The name is a string that identifies the value to the key. The length and the format of the value is dependent on the data type.
As you can see with the Registry Editor, the registry is divided into five principal keys: there is no way to add or delete keys at this level. Only two of these keys are effectively saved on hard disk: HKEY_LOCAL_MACHINE and HKEY_USERS. The others are jusr branches of the main keys or are dynamically created by Windows.

HKEY_LOCAL_MACHINE
This key contains any hardware, applications and services information. Several hardware information is updated automatically while the computer is booting. The data stored in this key is shared with any user. This handle has many subkeys:
Config
Contains configuration data for different hardware configurations.
Enum
This is the device data. For each device in your computer, you can find information such as the device type, the hardware manufacturer, device drivers and the configuration.
Hardware
This key contains a list of serial ports, processors and floating point processors.
Network
Contains network information.
Security
Shows you network security information.
Software
This key contains data about installed software.
System
It contains data that checks which device drivers are used by Windows and how they are configured.
HKEY_CLASSES_ROOT
This key is an alias of the branch HKEY_LOCAL_MACHINE\Software\Classes and contains OLE, drag'n'drop, shortcut and file association information.
HKEY_CURRENT_CONFIG
This key is also an alias. It contains a copy of the branch HKEY_LOCAL_MACHINE\Config, with the current computer configuration.
HKEY_DYN_DATA
Some information stored in the registry changes frequently, so Windows maintains part of the registry in memory instead of on the hard disk. For example it stores PnP information and computer performance. This key has two sub keys
Config Manager
This key contains all hardware information problem codes, with their status. There is also the sub key HKEY_LOCAL_MACHINE\Enum, but written in a different way.
PerfStats
It contains performance data about system and network

HKEY_USERS
This important key contains the sub key .Default and another key for each user that has access to the computer. If there is just one user, only .Default key exists. . Each sub key maintains the preferences of each user, like the desktop colors, the fonts used, and also the settings of many programs. If you open a user subkey you will find five important subkeys:
AppEvent
It contains the path of audio files that Windows plays when some events happen.
Control Panel
Here are the settings defined in the Control Panel. They used to be stored in win.ini and control.ini.
Keyboard Layouts
It contains some advanced code which identifies the actual keyboard disposition how it is set into the Control Panel.
Network
This key stores subkeys that describe current and recent network shortcuts.
RemoteAccess
The settings of Remote Access are stored here.
Software
Contains all software settings. This data was stored in win.ini and private .ini files.
HKEY_CURRENT_USER
It is an alias to current user of HKEY_USERS. If your computer is not configured for multi-users usage, it points to the subkey .Default of HKEY_USERS.

Description of .reg file
Here I am assuming that you already have a .reg file on your hard disk and want to know more about how it is structured.Now do not double click the .reg file or it's content will be added to the registry, of course there will be warning message that pops up. Now to view the properties of the .reg file open it in notepad.
To do so first launch notepad by going to Start>Programs>Accessories>Notepad.
Then through the open menu open the .reg file.
Now the thing that differentiates .reg files from other files is the word REGEDIT4. It is found to be the first word in all .reg files. If this word is not there then the registry editor cannot recognize the file to be a .reg file.
Then follows the key declaration which has to be done within square brackets and with the full path.If the key does not exist then it will be created.

After the key declaration you will see a list of values that have to be set in the particular key in the registry.The values look like this:
"value name"=type:value
Value name is in double commas. Type can be absent for string values, dword: for dword values and hex: for binary values. For all other values you have to use the code hex(#): , where # indicate the API code of the type.
So:
"My string" = "string value" is a string
"My dword" = dword:123456789 is a dword
"My binary" = hex:AA,BB,CC is a standard binary
"My other type" = hex(2):AA,BB,00 is an expand string
Important Note: expand string has API code = 2 and extended string has API code = 7.
As you can see, strings are in double quotes, dword is hexadecimal and binary is a sequence of hexadecimal byte pairs, with a comma between each. If you want to add a back slash into a string remember to repeat it two times, so the value "c:\Windows" will be "c:\\Windows".
Before write a new .reg file, make sure you do this else you will get an error message.
Command Line Registry Arguments
FILENAME.REG to merge a .reg file with the registry
/L:SYSTEM to specify the position of SYSTEM.DAT
/R:USER to specify the position of USER.DAT
/e FILENAME.REG [KEY] to export the registry to a file. If the key is specified, the whole branch will be exported.
/c FILENAME.REG to substitute the entire registry with a .reg file
/s to work silently, without prompt information or Warnings.

That wraps up the Windows Registry.

Reregister All .dll Files Within Registry

I ran across this the other day on another site and I thought that a couple people might find it helpful, so here we go:
1) First go Start/Run, and type in 'cmd' to bring up the Command Prompt.
2) Type 'CD \' and hit enter.
3) Type 'DIR *.dll /s /b > regdll.bat' and hit enter.
4) Type 'Notepad regdll.bat' and hit enter.
Now Notepad is going to bring up a list of your .dll files, nevermind that for a moment.
---
5) Now type 'Path' and hit enter to see your current path. It will bring up something like: Path=c:\Windows;c:\windows\Command
6) (supplement your Windows Version, ex: C:\WINNT, or C:\Windows) Now type: 'Path=c:\windows;c:\windows\Command;c:\Windows\Prog
ram~\Accessories' and hit enter.
7) Verify again by typing 'Path' and hitting enter, and then type: 'C:\WINNT\System32\Regsvr32.exe /s C:\' and hit enter again.
8) Now, go back to Notepad and if you have Win98 use the replace feature in Wordpad (CTRL + H) or notepad to search for 'C:\' and replace it with this: 'C:\Windows\System\Regsvr32.exe /s C:\'
If you have Win2000, etc. use the replace command in note pad to search for 'C:\' and replace it with this: 'C:\WINNT\System32\Regsvr32.exe /s C:\'
*Be sure to type the replace string exactly like above or it won't work*
9) Use "Replace All" to make the changes to the entire file.
10) When it finishes, save it, exit notepad or wordpad, and return to the Command Prompt.
11) Type 'regdll' and press enter. If you followed the above steps correctly it will now go through and re-register all your .dll files.

Safely editing..

Windows XP has a vast number of configuration dialogs, but some adjustments can be performed only by directly editing the Registry. Frequently, tips involving Registry tweaks include stern warnings to back up the Registry before making any change. The Windows XP Backup applet can back up the Registry along with other elements of the System State, but the resulting data file can occupy hundreds of megabytes. You're better off saving a system restore point each time you're about to edit the Registry. Better still, you can use Regedit to back up only the Registry keys that will be changed.
Click on Start | Run and enter Regedit to launch the Registry editor. To back up an individual key you plan to edit, navigate to the key and right-click on it. Choose Export from the menu, and save the key to a REG file. Open the REG file in Notepad and insert a few comment lines that describe the source and purpose of the tweak. (To create a comment line, simply put a semicolon at the start of the line.)
Now go ahead and make all the changes to Registry keys and values specified by the tip you're applying. Any time you add a new key or value, make a note of it with another comment line in the REG file. When you're done, save the REG file and close Notepad.
If later you want to undo this Registry tweak, just double-click on the REG file and confirm that you want to add it to the Registry. This will restore any deleted keys or values and will restore the original data for any values whose data was changed. Note that this will not remove new keys or values that were added; that's why you need to make comments about such changes.
Right-click on the REG file and choose Edit, which will open it in Notepad. Check for comments about keys or values that were added, and if you find any, use Regedit to delete them. You can delete the REG file itself once you've completed this process

Maintaining the Registry

How can you backup and restore the Registry?
Windows 95
Microsoft included a utility on the Windows 95 CD-ROM that lets you create backups of the Registry on your computer. The Microsoft Configuration Backup program, CFGBACK.EXE, can be found in the \Other\Misc\Cfgback directory on the Windows 95 CD-ROM. This utility lets you create up to nine different backup copies of the Registry, which it stores, with the extension RBK, in your \Windows directory. If your system is set up for multiple users, CFGBACK.EXE won't back up the USER.DAT file.
After you have backed up your Registry, you can copy the RBK file onto a floppy disk for safekeeping. However, to restore from a backup, the RBK file must reside in the \Windows directory. Windows 95 stores the backups in compressed form, which you can then restore only by using the CFGBACK.EXE utility.

Windows 98
Microsoft Windows 98 automatically creates a backup copy of the registry every time Windows starts, in addition to this you can manually create a backup using the Registry Checker utility by running SCANREGW.EXE from Start | Run menu.

What to do if you get a Corrupted Registry
Windows 95, 98 and NT all have a simple registry backup mechanism that is quite reliable, although you should never simply rely on it, remember to always make a backup first !

Windows 95

In the Windows directory there are several hidden files, four of these will be SYSTEM.DAT & USER.DAT, your current registry, and SYSTEM.DA0 & USER.DA0, a backup of your registry. Windows 9x has a nice reature in that every time it appears to start successfully it will copy the registry over these backup files, so just in case something goes wrong can can restore it to a known good state. To restore the registry follow these instruction:
[list=1]
* Click the Start button, and then click Shut Down.
* Click Restart The Computer In MS-DOS Mode, then click Yes.
* Change to your Windows directory. For example, if your Windows directory is c:\windows, you would type the following:
cd c:\windows
* Type the following commands, pressing ENTER after each one. (Note that SYSTEM.DA0 and USER.DA0 contain the number zero.)
attrib -h -r -s system.dat
attrib -h -r -s system.da0
copy system.da0 system.dat
attrib -h -r -s user.dat
attrib -h -r -s user.da0
copy user.da0 user.dat
* Restart your computer.
Following this procedure will restore your registry to its state when you last successfully started your computer.
If all else fails, there is a file on your hard disk named SYSTEM.1ST that was created when Windows 95 was first successfully installed. If necessary you could also change the file attributes of this file from read-only and hidden to archive to copy the file to C:\WINDOWS\SYSTEM.DAT.
Windows NT
On Windows NT you can use either the "Last Known Good" option or RDISK to restore to registry to a stable working configuration.
How can I clean out old data from the Registry?
Although it's possible to manually go through the Registry and delete unwanted entries, Microsoft provides a tool to automate the process, the program is called RegClean. RegClean analyzes Windows Registry keys stored in a common location in the Windows Registry. It finds keys that contain erroneous values, it removes them from the Windows Registry after having recording those entries in the Undo.Reg file.

Editing The Registry

The Registry Editor (REGEDIT.EXE) is included with most version of Windows (although you won't find it on the Start Menu) it enables you to view, search and edit the data within the Registry. There are several methods for starting the Registry Editor, the simplest is to click on the Start button, then select Run, and in the Open box type "regedit", and if the Registry Editor is installed it should now open and look like the image below.
An alternative Registry Editor (REGEDT32.EXE) is available for use with Windows NT/2000, it includes some additional features not found in the standard version, including; the ability to view and modify security permissions, and being able to create and modify the extended string values REG_EXPAND_SZ & REG_MULTI_SZ.
Create a Shortcut to Regedit
This can be done by simply right-clicking on a blank area of your desktop, selecting New, then Shortcut, then in the Command line box enter "regedit.exe" and click Next, enter a friendly name (e.g. 'Registry Editor') then click Finish and now you can double click on the new icon to launch the Registry Editor.
Using Regedit to modify your Registry
Once you have started the Regedit you will notice that on the left side there is a tree with folders, and on the right the contents (values) of the currently selected folder.

Like Windows explorer, to expand a certain branch (see the structure of the registry section), click on the plus sign [+] to the left of any folder, or just double-click on the folder. To display the contents of a key (folder), just click the desired key, and look at the values listed on the right side. You can add a new key or value by selecting New from the Edit menu, or by right-clicking your mouse. And you can rename any value and almost any key with the same method used to rename files; right-click on an object and click rename, or click on it twice (slowly), or just press F2 on the keyboard. Lastly, you can delete a key or value by clicking on it, and pressing Delete on the keyboard, or by right-clicking on it, and choosing Delete.
Note: it is always a good idea to backup your registry before making any changes to it. It can be intimidating to a new user, and there is always the possibility of changing or deleting a critical setting causing you to have to reinstall the whole operating system. It's much better to be safe than sorry!

Importing and Exporting Registry Settings
A great feature of the Registry Editor is it's ability to import and export registry settings to a text file, this text file, identified by the .REG extension, can then be saved or shared with other people to easily modify local registry settings. You can see the layout of these text files by simply exporting a key to a file and opening it in Notepad, to do this using the Registry Editor select a key, then from the "Registry" menu choose "Export Registry File...", choose a filename and save. If you open this file in notepad you will see a file similar to the example below:

Quote:
REGEDIT4
[HKEY_LOCAL_MACHINE\SYSTEM\Setup]
"SetupType"=dword:00000000
"CmdLine"="setup -newsetup"
"SystemPrefix"=hex:c5,0b,00,00,00,40,36,02
The layout is quite simple, REGEDIT4 indicated the file type and version, [HKEY_LOCAL_MACHINE\SYSTEM\Setup] indicated the key the values are from, "SetupType"=dword:00000000 are the values themselves the portion after the "=" will vary depending on the type of value they are; DWORD, String or Binary.
So by simply editing this file to make the changes you want, it can then be easily distributed and all that need to be done is to double-click, or choose "Import" from the Registry menu, for the settings to be added to the system Registry.
Deleting keys or values using a REG file
It is also possible to delete keys and values using REG files. To delete a key start by using the same format as the the REG file above, but place a "-" symbol in front of the key name you want to delete. For example to delete the [HKEY_LOCAL_MACHINE\SYSTEM\Setup] key the reg file would look like this:
Quote:
REGEDIT4
[-HKEY_LOCAL_MACHINE\SYSTEM\Setup]
The format used to delete individual values is similar, but instead of a minus sign in front of the whole key, place it after the equal sign of the value. For example, to delete the value "SetupType" the file would look like:
Quote:
REGEDIT4
[HKEY_LOCAL_MACHINE\SYSTEM\Setup]
"SetupType"=-
Use this feature with care, as deleting the wrong key or value could cause major problems within the registry, so remember to always make a backup first.
Regedit Command Line Options
Regedit has a number of command line options to help automate it's use in either batch files or from the command prompt. Listed below are some of the options, please note the some of the functions are operating system specific.

 

* regedit.exe [options] [filename] [regpath]
* [filename] Import .reg file into the registry
* /s [filename] Silent import, i.e. hide confirmation box when importing files
* /e [filename] [regpath] Export the registry to [filename] starting at [regpath]
e.g. regedit /e file.reg HKEY_USERS\.DEFAULT
* /L:system Specify the location of the system.dat to use
* /R:user Specify the location of the user.dat to use
* /C [filename] Compress (Windows 98)
* /D [regpath] Delete the specified key (Windows 98)

How to Backup the Registry

Before you edit the registry, export the keys in the registry that you plan to edit, or back up the whole registry. If a problem occurs, you can then follow the steps how-to restore the registry to its previous state.
How to Export Registry Keys
Click Start, and then click Run.
In the Open box, type regedit, and then click OK.
On the File menu, click Export.
In the Save in box, select the boxs at the bottom the bottom according to weather you want to export all or only selected branches of the registry.
Next select a location in which to save the backup .reg file.
In the File name box, type a file name, and then click Save.

How to Restore the Registry
To restore registry keys that you exported, double-click the .reg file that you saved.

What is the Registry ?

What is the Registry?

The Registry is a database used to store settings and options for the 32 bit versions of Microsoft Windows including Windows 95, 98, ME and NT/2000. It contains information and settings for all the hardware, software, users, and preferences of the PC. Whenever a user makes changes to a Control Panel settings, or File Associations, System Policies, or installed software, the changes are reflected and stored in the Registry.
The physical files that make up the registry are stored differently depending on your version of Windows; under Windows 95 & 98 it is contained in two hidden files in your Windows directory, called USER.DAT and SYSTEM.DAT, for Windows Me there is an additional CLASSES.DAT file, while under Windows NT/2000 the files are contained seperately in the %SystemRoot%\System32\Config directory. You can not edit these files directly, you must use a tool commonly known as a "Registry Editor" to make any changes (using registry editors will be discussed later in the article).
The Structure of The Registry
The Registry has a hierarchal structure, although it looks complicated the structure is similar to the directory structure on your hard disk, with Regedit being similar to Windows Explorer.
Each main branch (denoted by a folder icon in the Registry Editor, see left) is called a Hive, and Hives contains Keys. Each key can contain other keys (sometimes referred to as sub-keys), as well as Values. The values contain the actual information stored in the Registry. There are three types of values; String, Binary, and DWORD - the use of these depends upon the context.

There are six main branches, each containing a specific portion of the information stored in the Registry. They are as follows:
* HKEY_CLASSES_ROOT - This branch contains all of your file association mappings to support the drag-and-drop feature, OLE information, Windows shortcuts, and core aspects of the Windows user interface.
* HKEY_CURRENT_USER - This branch links to the section of HKEY_USERS appropriate for the user currently logged onto the PC and contains information such as logon names, desktop settings, and Start menu settings.
* HKEY_LOCAL_MACHINE - This branch contains computer specific information about the type of hardware, software, and other preferences on a given PC, this information is used for all users who log onto this computer.
* HKEY_USERS - This branch contains individual preferences for each user of the computer, each user is represented by a SID sub-key located under the main branch.
* HKEY_CURRENT_CONFIG - This branch links to the section of HKEY_LOCAL_MACHINE appropriate for the current hardware configuration.
* HKEY_DYN_DATA - This branch points to the part of HKEY_LOCAL_MACHINE, for use with the Plug-&-Play features of Windows, this section is dymanic and will change as devices are added and removed from the system.

 

Each registry value is stored as one of five main data types:
* REG_BINARY - This type stores the value as raw binary data. Most hardware component information is stored as binary data, and can be displayed in an editor in hexadecimal format.
* REG_DWORD - This type represents the data by a four byte number and is commonly used for boolean values, such as "0" is disabled and "1" is enabled. Additionally many parameters for device driver and services are this type, and can be displayed in REGEDT32 in binary, hexadecimal and decimal format, or in REGEDIT in hexadecimal and decimal format.
* REG_EXPAND_SZ - This type is an expandable data string that is string containing a variable to be replaced when called by an application. For example, for the following value, the string "%SystemRoot%" will replaced by the actual location of the directory containing the Windows NT system files. (This type is only available using an advanced registry editor such as REGEDT32)
* REG_MULTI_SZ - This type is a multiple string used to represent values that contain lists or multiple values, each entry is separated by a NULL character. (This type is only available using an advanced registry editor such as REGEDT32)
* REG_SZ - This type is a standard string, used to represent human readable text values.
Other data types not available through the standard registry editors include:
* REG_DWORD_LITTLE_ENDIAN - A 32-bit number in little-endian format.
* REG_DWORD_BIG_ENDIAN - A 32-bit number in big-endian format.
* REG_LINK - A Unicode symbolic link. Used internally; applications should not use this type.
* REG_NONE - No defined value type.
* REG_QWORD - A 64-bit number.
* REG_QWORD_LITTLE_ENDIAN - A 64-bit number in little-endian format.
* REG_RESOURCE_LIST - A device-driver resource list.