Creating a mandatory profile will do what you are looking for...
You will need to login with a different user credentials.
In windows explorer Drill down to X:\Documents And Settings\Nameoftheuser
There's a hidden file called NTUSER.DAT rename it to NTUSER.MAN.
Logooff an login with the user whose profile you have just altered, do any system wide changes you like, restart or logoff and login again kaboom all settings are back to default.
From command prompt you can do the same go to command prompt and paste the following :-
CD "Document and settings"
CD Administrator
ren ntuser.dat ntuser.man
Would suggest to make the desired changes to the profile before renaming the file...