How to recover from a corrupted registry that prevents Windows XP from starting

Part one

In part one, you start the Recovery Console, create a temporary folder, back up the existing registry files to a new location, delete the registry files at their existing location, and then copy the registry files from the repair folder to the System32\Config folder. When you have finished this procedure, a registry is created that you can use to start Windows XP. This registry was created and saved during the initial setup of Windows XP. Therefore any changes and settings that occurred after the Setup program was finished are lost.

To complete part one, follow these steps:

1.	Insert the Windows XP startup disk into the floppy disk drive, or insert the Windows XP CD-ROM into the CD-ROM drive, and then restart the computer. Click to select any options that are required to start the computer from the CD-ROM drive if you are prompted to do so.
2.	When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
3.	If you have a dual-boot or multiple-boot computer, select the installation that you want to access from the Recovery Console.
4.	When you are prompted to do so, type the Administrator password. If the administrator password is blank, just press ENTER.
5.	At the Recovery Console command prompt, type the following lines, pressing ENTER after you type each line: md tmp copy c:\windows\system32\config\system c:\windows\tmp\system.bak copy c:\windows\system32\config\software c:\windows\tmp\software.bak copy c:\windows\system32\config\sam c:\windows\tmp\sam.bak copy c:\windows\system32\config\security c:\windows\tmp\security.bak copy c:\windows\system32\config\default c:\windows\tmp\default.bak delete c:\windows\system32\config\system delete c:\windows\system32\config\software delete c:\windows\system32\config\sam delete c:\windows\system32\config\security delete c:\windows\system32\config\default copy c:\windows\repair\system c:\windows\system32\config\system copy c:\windows\repair\software c:\windows\system32\config\software copy c:\windows\repair\sam c:\windows\system32\config\sam copy c:\windows\repair\security c:\windows\system32\config\security copy c:\windows\repair\default c:\windows\system32\config\default
6.	Type exit to quit Recovery Console. Your computer will restart.

Note This procedure assumes that Windows XP is installed to the C:\Windows folder. Make sure to change C:\Windows to the appropriate windows_folder if it is a different location.

If you have access to another computer, to save time, you can copy the text in step two, and then create a text file called "Regcopy1.txt" (for example). To create this file, run the following command when you start in Recovery Console:

batch regcopy1.txt

With the batch command in Recovery Console, you can process all the commands in a text file sequentially. When you use the batch command, you do not have to manually type as many commands.

Part two

To complete the procedure described in this section, you must be logged on as an administrator, or an administrative user (a user who has an account in the Administrators group). If you are using Windows XP Home Edition, you can log on as an administrative user. If you log on as an administrator, you must first start Windows XP Home Edition in Safe mode. To start the Windows XP Home Edition computer in Safe mode, follow these steps.

Note Print these instructions before you continue. You cannot view these instructions after you restart the computer in Safe Mode. If you use the NTFS file system, also print the instructions from Knowledge Base article KB309531. Step 7 contains a reference to the article.

1.	Click Start, click Shut Down (or click Turn Off Computer), click Restart, and then click OK (or click Restart).
2.	Press the F8 key. On a computer that is configured to start to multiple operating systems, you can press F8 when you see the Startup menu.
3.	Use the arrow keys to select the appropriate Safe mode option, and then press ENTER.
4.	If you have a dual-boot or multiple-boot system, use the arrow keys to select the installation that you want to access, and then press ENTER.

In part two, you copy the registry files from their backed up location by using System Restore. This folder is not available in Recovery Console and is generally not visible during typical usage. Before you start this procedure, you must change several settings to make the folder visible:

1.	Start Windows Explorer.
2.	On the Tools menu, click Folder options.
3.	Click the View tab.
4.	Under Hidden files and folders, click to select Show hidden files and folders, and then click to clear the Hide protected operating system files (Recommended) check box.
5.	Click Yes when the dialog box that confirms that you want to display these files appears.
6.	Double-click the drive where you installed Windows XP to display a list of the folders. If is important to click the correct drive.
7.	Open the System Volume Information folder. This folder is unavailable and appears dimmed because it is set as a super-hidden folder. Note This folder contains one or more _restore {GUID} folders such as "_restore{87BD3667-3246-476B-923F-F86E30B3E7F8}". Note You may receive the following error message: C:\System Volume Information is not accessible. Access is denied. If you receive this message, see the following Microsoft Knowledge Base article to gain access to this folder and continue with the procedure: 309531 How to gain access to the System Volume Information folder
8.	Open a folder that was not created at the current time. You may have to click Details on the View menu to see when these folders were created. There may be one or more folders starting with "RPx under this folder. These are restore points.
9.	Open one of these folders to locate a Snapshot subfolder. The following path is an example of a folder path to the Snapshot folder: C:\System Volume Information\_restore{D86480E3-73EF-47BC-A0EB-A81BE6EE3ED8}\RP1\Snapshot
10.	From the Snapshot folder, copy the following files to the C:\Windows\Tmp folder: • _REGISTRY_USER_.DEFAULT • _REGISTRY_MACHINE_SECURITY • _REGISTRY_MACHINE_SOFTWARE • _REGISTRY_MACHINE_SYSTEM • _REGISTRY_MACHINE_SAM
11.	Rename the files in the C:\Windows\Tmp folder as follows: • Rename _REGISTRY_USER_.DEFAULT to DEFAULT • Rename _REGISTRY_MACHINE_SECURITY to SECURITY • Rename _REGISTRY_MACHINE_SOFTWARE to SOFTWARE • Rename _REGISTRY_MACHINE_SYSTEM to SYSTEM • Rename _REGISTRY_MACHINE_SAM to SAM

These files are the backed up registry files from System Restore. Because you used the registry file that the Setup program created, this registry does not know that these restore points exist and are available. A new folder is created with a new GUID under System Volume Information and a restore point is created that includes a copy of the registry files that were copied during part one. Therefore, it is important not to use the most current folder, especially if the time stamp on the folder is the same as the current time.

The current system configuration is not aware of the previous restore points. You must have a previous copy of the registry from a previous restore point to make the previous restore points available again.

The registry files that were copied to the Tmp folder in the C:\Windows folder are moved to make sure that the files are available under Recovery Console. You must use these files to replace the registry files currently in the C:\Windows\System32\Config folder. By default, Recovery Console has limited folder access and cannot copy files from the System Volume folder.

Note The procedure described in this section assumes that you are running your computer with the FAT32 file system.

For additional information about how to access the System Volume Information Folder with the NTFS file system, click the following article number to view the article in the Microsoft Knowledge Base:

309531 How to gain access to the System Volume Information folder

Part Three

In part three, you delete the existing registry files, and then copy the System Restore Registry files to the C:\Windows\System32\Config folder:

1.	Start Recovery Console (or by using a Windows 98 Boot Disk).
2.	At the command prompt, type the following lines, pressing ENTER after you type each line: del c:\windows\system32\config\sam del c:\windows\system32\config\security del c:\windows\system32\config\software del c:\windows\system32\config\default del c:\windows\system32\config\system copy c:\windows\tmp\software c:\windows\system32\config\software copy c:\windows\tmp\system c:\windows\system32\config\system copy c:\windows\tmp\sam c:\windows\system32\config\sam copy c:\windows\tmp\security c:\windows\system32\config\security copy c:\windows\tmp\default c:\windows\system32\config\default Note Some of these command lines may be wrapped for readability.
3.	Type exit to quit Recovery Console. Your computer restarts.

Note This procedure assumes that Windows XP is installed to the C:\Windows folder. Make sure to change C:\Windows to the appropriate windows_folder if it is a different location.

If you have access to another computer, to save time, you can copy the text in step two, and then create a text file called "Regcopy1.txt" (for example).

Part Four

1.	Click Start, and then click All Programs.
2.	Click Accessories, and then click System Tools.
3.	Click System Restore, and then click Restore to a previous RestorePoint.

Cannot Start Windows XP if the System or Software Hive Is Missing or Damaged (Q303012)

SYMPTOMS
When you try to start or restart your Windows XP-based computer, you may receive one of the following error messages:

Windows XP could not start because the following file is missing or corrupt: \WINDOWS\SYSTEM32\CONFIG\SYSTEM

Windows XP could not start because the following file is missing or corrupt: \WINDOWS\SYSTEM32\CONFIG\SOFTWARE

Stop: c0000218 {Registry File Failure} The registry cannot load the hive (file): \SystemRoot\System32\Config\SOFTWARE or its log or alternate

CAUSE
This issue can occur if the System or Software hive for the Windows XP installation is missing or damaged.

RESOLUTION
To resolve this issue, use one of the following methods.

Use the Recovery Console Tool
To restore a damaged registry hive, use the Recovery Console to restore the backup copy of the hive from the Repair folder. The Repair folder contains a copy of the system's registry hives that were created after the first successful startup of Windows XP.

WARNING : Although data should not be affected by the following procedure, you may need to restore changes you previously made to programs or system settings since the first time you successfully started Windows XP.

To replace the damaged registry hive and restore the backup copy of the hive from the Repair folder: Start your computer to the Recovery Console.

Determine if the file that is mentioned in the "Symptoms" section of this article is present, and if it is, rename it:

In Recovery Console, change to the c:\Windows folder.

Type cd sytem32\config , and then press ENTER.

Type dir system , and then press ENTER.

If you cannot run the preceding command successfully (because the file is missing), skip to step 3. If you can run the preceding command successfully, type ren system system.bak , and then press ENTER.

NOTE : If the message that you received referred to the software file, replace "system" with "software" in the preceding command. For example, you would type ren software software.bak (instead of ren system system.bak ), and then press ENTER.

Type copy c:\windows\repair\system , and then press ENTER.

NOTE : If the message that you received referred to the software file, replace "system" with "software" in the preceding command. For example, you would type copy c:\windows\repair\software (instead of copy c:\windows\repair\system ), and then press ENTER.

You should receive a "One file copied" informational message. For additional information about how to use Recovery Console during startup, click the article number below to view the article in the Microsoft Knowledge Base:
Q307654 HOW TO: Install and Use the Recovery Console for Windows XP


IMPORTANT : If you encounter problems when you run the preceding commands, you may need to use the Change Directory command ( cd ) one folder at a time before you run the preceding commands. For example, type cd system32 , press ENTER, type cd config , and then press ENTER.

Type exit , and then press ENTER to quit Recovery Console and restart the computer.

You Cannot Start from the Windows XP CD-ROM or Use Recovery Console
If you cannot start from the Windows XP CD-ROM or use Recovery Console and you are using the FAT file system (not the NTFS file system):
Use a startup disk from one of the following operating systems to start your computer to a command prompt:

quick launch disappears each reboot (xp)

option 1

to permanently set the quick launch bar so that it doesn't disappear:

HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon

Name: Userinit
Data: %system32%\wsaupdater.exe,

Instead of wsaupdater.exe, the data should contain userinit.exe, (including the comma at the end).

the data should now read: C:\Windows\System32\userinit.exe.

Make the change accordingly

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option 2

1) Run 'Regedit'. Browse to the following registry location: HKEY_CURRENT_USER\software\microsoft\windows\currentverion\polices\explorer

2) Locate the Registry entry 'NoSaveSettings'and double-click to bring up the 'Edit DWORD value' diaglog

3) Change the 'Value Data' from '1' to '0' (i.e. where 0 = Explorer Settings - including Quick Launch Settings - are saved)

4) Close Regedit

5) Restart the Computer

6) Ensure that the Quick Launch Toolbar is displayed (Right-click anywhere on the toolbar to bring properties and check 'Show Quick Launch Toolbar'.

7) Restart the Computer

Note: The 2 restarts are necessary in order to actually see the changed behaviour. The first restart saves the registry change so that Explorer settings (such as Quick Launch settings) are saved during the second and all subsequent restarts.

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option 3

This can happen if something, like Tweakui, creates a ClassicShell value name at HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer and sets it to 0x0000.

To fix the problem, delete the ClassicShell value name, and restart your computer.