I created a "test" NT 4.0 PDC and made is master of a "test" domain because I wanted to test an upgrade I was going to perform on our real PDC. Everything went fine, so now I want to remove the "test" domain from the list under "Microsoft Windows Network", since our company has several domains I don't want people getting confused and trying to access this test domain. Is there a way I can remove it from the list easily? Or do I have to wait a set amount of time?

Just take the PDC off the network and the browser service will eventually drop it. But, also check your any WINS database you have and delete any referances, or listing that you might have made in DNS.