I have a mixture of Windows 2000 servers and NT servers. My DNS server is Win2k. I would like to create an Active Directory environment on the DNS server, then simply change the existing domain name on all servers and PCs to the new domain created by AD. Is it possible to change the domain on a Win2k server so it joins the new AD domain, or do I have to rebuild it to make it a member of the new domain?
If I understand correctly, you want to build a new AD and migrate all existing servers to it. If you have an existing AD that you will not be using anymore, all that you have to do is DCPROMO and demote the current Windows 2000 DCs and then run DCPROMO again and tell them to join the new domain that you created.
Keep in mind that if you want the user accounts to move to the new domain you should establish a trust between the two domains and use ADMT (Active Directory Migration Tool) to migrate the accounts prior to demoting all of the existing DCs in the old domain.