I am having difficulty installing a Windows 2008 R2 domain controller into an existing domain. When I run dcpromo.exe, I get an error message saying "To intall a domain contoller into an Active Directory domain, you must firest prepare the domain using "adprep /domainprep". The Adprep utility is available on the Windows Server 2008 R2 installation media in the \support\adprep folder.
So I went to an existing domain contoller and ran adprep /domainprep from the Win 2K8 R2 DVD and I get the following:
Running domainprep ...
Domain-wide information has already been updated.
Adprep did not attempt to rerun this operation.
I then go back to my original server and run dcpromo, and I get the same message all over again. Ideas? (Yes, I have run forestprep from the same R2 install media)