When you upgrade Windows NT 4.0 BDC, restart the newly upgraded Windows 2000 Server, and begin the DCPromo process, you receive:
The domain <DomainName> is not an Active Directory domain, or an Active Directory domain controller for the domain could not be contacted.
This error is reported when you select the Leave as member server option, but DCPromo works if you select the Make a Domain Controller option.
This behavior is probably the result of invalid entries for domain controllers in the %SystemRoot%\System32\Drivers\Etc\LMHOSTS file.
To fix the problem, correct or remove the invalid entries.
NOTE: The incorrect entry is probably the first n.n.n.nBDCname #PRE #DOM:DomainName entry, where n.n.n.n is the IP address.