"Registry Editing is Disabled"

This error occurs if the DisableRegistryTools Policy is enabled. With this policy enabled, you receive the following error message when you start the Registry Editor (regedit.exe):
Registry Editing has been disabled by your administrator

IMPORTANT: If this policy was enabled in your system (not connected to a corporate network) without you doing anything or without your knowledge, then it's highly likely that a Virus has blocked the usage of Registry Editor (Regedit.exe) in your system by enabling the DisableRegistryTools policy via the registry. It's highly recommended that you perform a thorough checkup of your system immediately. Steps listed in this article will help you unblock the Registry Editor, but that does not remove the Virus (if any) from your system.

For standalone Windows XP systems, perform the steps below to remove the registry editing restrictions.
Method 1: Using the REG.EXE console tool
1. Click Start, Run and type this command:

REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools /t REG_DWORD /d 0 /f

You should be able to launch Tweak UI, as well as the Registry Editor.

Method 2: Using the Group Policy Editor (Windows XP Professional only)
->Click Start, Run and type gpedit.msc and press ENTER
-> Go to the following location:

User Configuration Administrative Templates System

-> Double-click Disable registry editing tools and set it to Not Configured
-> Exit the Group Policy Editor

Note: If the setting already reads Not Configured, set it to Enabled, and click Apply. Then revert it back to Not Configured. This ensures that the DisableRegistryTools registry value is removed successfully.