I've found a way to disable Parental Controls in Vista, if your account has been restricted. Go to Start > Run (if you can't find it, just press the Windows key + R). Then enter the command NET STOP "Parental controls". That should disable it. (I just needed to post this )
Ah, I ust thought it might of had something to do with the .NET Framework like the Parental Controls relying on it so when you stop it then the Parental Controls stopped.