local/domain user rights

I have around 40 users on my network, all have domain user logins of course, and their workstations are NT4 boxes on which they do not have a local login. The only local login is the admin account used to set up the machines. How do I give a particular person local admin rights to their machine without affecting their domain login? I guess this means having user-priveleges on the network AND local-admin rights at the same time, is this possible?