Windows 2000 permisions on Workstations

I have Win.2000 Wk. running on an NT 4.0 domain. I have noticed that when a user loggins into the domain. They do not have sufficient rights to run certain programs, one example is Netscape. The only solution that I have found is to give them admin.privliages on the local machine, but I do not want to do this. Any suggestions?