We're trying to get to a 2003 domain by upgrading an existing NT 4.0 domain controller. The 2003 server disk we have is for new installations only, but we have 2000 server disks and have sucessfully upgraded an NT 4.0 PDC to windows 2000 (off the network). I'm wondering if we can add a 2003 domain controller to the 2000 server domain and then retire the 2000 server or keep it on if that's not a problem. Also, would it make any difference if we left the NT 4.0 BDCs on line during each of these steps? And what about the clients would they accept this process or do we need to disjoin and rejoin them to the domain at any point for them to work with Active directory? I know the clients need to have their TCP/IP settings updated for the new DC/ DNS server.