Administrator of a Local PC on a Domain

I have several Windows 2000 and XP systems on a Windows 2000 domain. I’m trying to allow the PC’s user to be an administrator on their own local PC. Their userid is NOT an administrator on the Windows 2000 server. How can I get their account to administer their local PC without giving admin rights to the Windows 2000 server? On one system we renamed the administrator id, but I don’t know if that was a good idea. Thanks in advance.