I never got this problem before. We just switch our ISP so we requested to add our existing dns server record pointed to this win2k server. This is the only server has AD/DNS/IIS/SQL installed. For example, we have testdomain.com as public and private doamin name. Even I try to demote and re-promote DC to different domain name than public name, like testdom without .com, and try to join this new domain from all the workstation(Win ME, 2000). None of them could not able to join to this new domain either. Please help me from this weird situations. Thanks.