Win 2000 pro

I need a little help ….I’m trying to join a Win 2000 professional client to a Win server 2003 domain . I’ve installed WINS on my 20003 server , but i’m not sure what do next …..I’ve tried joining the client to the domain and it’s unable to join …..I read something saying that the domain functional level could be an issue. I’m a little lost right now …..My domain function level is at its highest .