Local Administrator Group Reg Location

My home comuter is on the company domain for easy of use but I'd like to stop the domain or any other GP or program from adding domain or local users to the Local Administrators Group. What area of the registry do I need to monitor to check for changes to that group. I've tried to manually add and subtract users to that group and see what keys are changing but not having much luck. Thanks for any help.

 

I think you'll be deceived...
Out of the testing i've made it appears that user account information are stored in a file called activeds.tlb wich is a Active DS Type Library and thus not in registry.