windows rights?

Strange situation…recently upgraded domain from NT to 03. Our win xp systems are having trouble running a certain ap when users are logged in that do not have extended rights. If I make the user a Power user on that system, then all is well. Also, if I open explorer as such a user, I can browse to where the data is, but if I go to teh address bar and put in teh drive letter: then it says access denied. I suspect this is due to some havoc wreaked on teh registry by our old ntconfig.pol policy file (which I have killed) but I can’t figure out how to undo it. ??