When you run Dcpromo.exe to configure this domain controller, it configures as a member server?
When you attempt to promote it to a domain controller, you receive:
The primary domain controller of the domain to which this computer belongs has not been converted to an Active Directory domain controller. You must convert the primary domain controller before you can install additional domain controllers for that domain.
If you had NetWare Directory Services (NDS) installed on the Windows NT 4.0 PDC, and did NOT uninstall it, prior to the upgrade, the above condition will happen.
You must remove NDS prior to the upgrade of a Windows NT 4.0 domain controller.