Update Windows 2008 R2 server to Domain Controller

Have 2 Windows 2008 (32 bit) servers as Domain Controllers.  Running Windows 2008 Functional level

Have a Windows 2008 R2 (64 bit) server I want to add as a domain controller.

When I run dcpromo it says to run adprop/forestprep.

When I run that on  a DC I get the message the domain has already been prepared.

How do I promote the server to a DC.

Thanks

Dave

Dave Kozlowski