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If a computer no longer boots up, often a rogue Registry setting is the culprit. In these cases you need an offline Registry editor, that is you have to edit the Registry from a second installation. Although there are third party offline Registry editors, you can use regedit as an offline Registry editor. The procedure described here also works with Windows PE (Windows Preinstallation Environment) or Windows RE (Windows Recovery Environment).
Prepare Windows RE or Windows PE ^
- Windows RE: You only need a Windows 7 or Windows Vista installation DVD. After you boot from the DVD, click "Next," then click "Repair your computer," then click "Next" (Use recovery tools), and then "Command Prompt."
- Windows PE: You can also use Windows PE to launch an offline Registry editor. Check out my article about creating a bootable WinPE USB flash drive for more information.
Use regedit as offline Registry editor ^
- Launch regedit on the command prompt.
- Click HKEY_LOCAL_MACHINE.
- In the File menu, click "Load Hive."
- Open the database file that contains the Registry hive you need:
- HKEY_LOCAL_MACHINE \SAM = %windir%\system32\config\SAM
- HKEY_LOCAL_MACHINE \SYSTEM = %windir%\system32\config\SYSTEM
- HKEY_LOCAL_MACHINE \SOFTWARE = %windir%\system32\config\SOFTWARE
- HKEY_USERS \.Default = %windir%\system32\config\DEFAULT
- HKEY_CURRENT_USER = %userprofile%\ntuser.dat
- Enter an arbitrary key name when prompted. A new node with your key name appears under HKEY_LOCAL_MACHINE.
- Edit the Registry entries in the new node.
- Click the root folder of your node, and then click "Unload hive" in the File menu. Your changes will be written to the offline Registry.
Note that you can import and export .reg files to the offline Registry edtior. This allows you to use Registry settings from another machine for troubleshooting purposes.
Also note that this procedure can be used to edit the settings of a user profile without logging on with the corresponding user account. In one of my next posts, I will show you how you can—through offline Registry editor—access a computer where you have forgotten the administrator password, without requiring third-party software.