Make a backup of ur registry 1st... either with some sw like system mechanic.. or by directly run "regedit"... Registry->Export Registry File, save under some name.
Then
goto
[HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVe rsionPoliciesWinOldApp]
delete registry item "Disabled"=dword:0
[HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVe rsionPoliciesSystem]
delete registry item "DisableRegistryTools"=dword:0
That might help. Don't worry of problems. U can always get back old registry settings by runnin the registry file u just backed up 1st.
If nuthin works.. open computer in safe mode & run the same registry file u backed up.
Or do as SwattyCatty said...