DNS NAME DOES NOT EXIST...vista business computer w/windows 2000 server?

When I tried adding a user to my domain under administrator I received the error DNS name does not exist. I have a windows 2000 server and the computer is a dell w/vista business. I already added two other emachines w/vista business to the domain so i know it is not a Vista compatability issue. The only difference is that the dell came w/vista business pre-installed, where with the e-machines I upgraded them from Vista Home Premium to Vista Business. Please help?

Did you really mean adding a machine not adding a user?

Make sure those machines set to "Register name with DNS". Also make sure DNS is running. Finally make sure the name doesn't already exist in DNS.