When you use Dcpromo to demote a Windows Server 2003 domain controller, you receive:
This domain controller holds the last replica of the following naming contexts:
If you used the Configure Your Server wizard to install the domain controller, it automatically creates a program partition or a non-domain naming context called DC=MSTAPI,DC=yourDomainName,DC=COM.
If the name os MSTAPI and it is not in use, you can remove it with the following command:
tapicfg remove /directory:mstapi.yourDomainName.com
If the partition was created by another program, or you created it manually, use Ntdsutil to remove it:
1. Open a CMD prompt and type ntdsutil.
2. At the Ntdsutil: prompt, type domain management.
3. At the domain management: prompt, type connections.
4. Type connect to server YourServerName.
5. After the binding message, you should see a successful connection to your server.
6. Type quit at the Server Connections prompt.
7. Type list at the domain management: prompt.
8. To remove the DC=MyNC,DC=yourDomainName,DC=COM naming context, type remove NC DC=MyNC,DC=yourDomainName,DC=COM.
9. Type q and press Enter until you are returned the the CMD prompt.
NOTE: You may have to restart your domain controller before you can demote it using Dcpromo.