Symptom
When you run the Tweak UI PowerToy for Windows XP, the following message may be displayed:

Tweak UI has been disabled by your administrator.

More information
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 […]

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There is a registry hack to enable or disable Windows NT TaskManager. The same registry hack applies to Windows 2000 and Windows XP.
Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Policies\System
Name: DisableTaskMgr
Type: REG_DWORD
Value: 1=Enable this key, that is DISABLE TaskManager
Value: 0=Disable this key, that is Don’t Disable, Enable TaskManager
As part of the enhanced […]

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