You need to complete the AD install by running the wizard (start->run->dcpromo). I'm assuming that you cancelled out of the wizard that comes after the win2k install is completed.
You cannot have a Win2k DC with Active Directory. If you insist on a WinNT domain, then you need complete the AD domain upgrade, and then demote the AD server to a member server. do this with the BDC offline, and then promote the BDC to a PDC (while still offline or unplugged from the network).
Once you are done with that, delete the computer account for your old PDC (from server manager) and then connect the new PDC to the network.
Finally, recreate the old PDC (now a Win2K server) computer account.