Windows 2000 Server

I had a windows nt4.0 server, I now have a windows 2000 server and we now migrated to another hardware running windows 2000 server. The windows nt4.0 server is off the network. When you log into a workstation that is attached to the network and in the Domain list it shows Local administrator,Windows 2000 server and Windows nt 4.0 in the list. How can I remove the old windows nt 4.0 from the Domain list when loggin into windows 2000 domain? Help!