There's nothing you should need from NSLOOKUP to join a computer or server to an existing domain and network. If you have a functional domain that has DHCP configured already then all you need to do is go to "Control Panel", "System", and on the "General" tab click "Change" and in the "Member of" select "Domain" and type your domain credentials to join the domain. I would recommend you give the server a meaningful name and probably be a good idea to set a static IP address, Gateway, and DNS servers on this server which I'm guessing is a test server? You do have the domain administrator password and permission to join a server to this domain?