2) Click the Run Command
3) In the Run Command Windows type "regedt32"
4) Navigate to each of the following areas and change the value as listed:
[HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Policies\System]
Set "DisableTaskMgr"=dword:00000000
[HKEY_CURRENT_USER\Software\Microsoft\Windows\
CurrentVersion\Group PolicyObjects\LocalUser\Software\
Microsoft\Windows\CurrentVersion\Policies\System]
Set "DisableTaskMgr"=dword:00000000
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrentVersion\policies\system\]
Set "DisableTaskMgr"=dword:00000000
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\
CurrentVersion\Winlogon]
Set "DisableCAD"=dword:00000000
5) Restart the computer
6) Task Manager should be enabled
Recommended Tools:
-For an automatic fix try this custom registry file

See Also:
-Registry Editing Disabled By Administrator
http://ultcomprepair.blogspot.com/2008/07/registry-editing-disabled-by.html