Logging into XP without connecting into the server

I had to set up an old computer thats been sitting in the corner for quite sometime. I hooked it all up. Once I ran the computer it was already set up as a domain workstation. I do not want to connect it to the server. How do I log into the PC and change its settings without connecting to the server? It will not take my admin logging info. If I do connect it to the server it will not establish a connection because I think the TCP/IP settings are not correct. Am I going to have to reinstall windows?