Permissions and access to controls

I am running a small office network in my home, all 3 desktop PCs are running Windows XP Pro I am the admin on all 3 of the units, I have a problem with my doughter that is constently locking down her security settings on her PC
and then can not access the internet when she need to. Now I’m not an IT Pro. however I am verry comfertable working in the regestory when needed.
The question: how can I lock her out of the security setting or restrict her ability to change the security settings? she is the only user on her pc, she knows just enough to be a detrament to herself and a pain for me.

Thank you in advavce
TDWay A Faithfull Reader