When you promoted your Windows 2000 Server to a domain controller, you entered a Directory Service Restore Mode Administrator password, which is used by the Recovery Console.
The Directory Service Restore Mode Administrator password is separate from the Administrator password that is stored in the Active Directory.
It is stored in the local SAM, %SystemRoot%\System32\Config\SAM. To change it:
1. Shutdown and restart.
2. Press F8 for advanced startup options.
3. Select the Directory Service Restore Mode.
4. Log on.
5. Use the Local User and Groups snap-in or type net user Administrator *.
6. Shutdown and restart.
If you forget the password, you will NOT be able to use the Directory Service Restore Mode, unless:
1. Perform an alternate install to a different drive, using a new computer name. You can install Professional.
2. Copy the original installs %SystemRoot%\Repair\SAM to the original %SystemRoot%\System32\Config\SAM.
NOTE: You must remember the original Windows 2000 Server's Administrator password. If you don't, demote the domain controller and re-promote it.