In the last resort (if control panel is restricted too) you can run RESTrick in the following way:
open the Windows system folder (ex. c:\windows\system) and double-click rest2.cpl file.
You can uninstall RESTrick manually too. For this open your system folder in the Explorer, find the file "REST2.CPL" and delete it.
However if you require to remove restrictions that have been installed with RESTrick you should do it before uninstall since they are Windows based, so simply uninstalling RESTrick is insufficient.