Lost Administrator Privileges !!!

Windows XP Media Center Home Version - service pack 2 system.

Somehow or other I'm locked out of Control Panel and all it's functions.
I have no idea how this happened and wonder if I can restore this very
important feature.

No matter how I log on, none of my logon names can address these
features.

When openingExplorer, and double clicking Windows\system32\control.exe,
it brings up the same window declaring "This operation has been cacelled
due to restrictions in effect on this computer. Please contact your
system administrator" Frustrating.......

Anyone with the knowledge to hack what ever is necessary to clear
these restrictions would be greatly appreciated. I am not afraid of
working in the registry, just don't have any idea where or what syntax
it takes to do the restoration.

Any constructive info would be greatly appreciated.