I have a Windows 2003 domain controller and am adding a new Windows 2008 R2 64-bit domain controller to the environment. I used the Windows 2008 R2 CD and ran adprep /forestprep, adprep /domainprep, adprep /gpprep, etc. and all was fine. When I try to add the 2008 server to the domain using dcpromo it says that the forest must be prepared by running adprep /forestprep. If I re-run adprep /forestprep on the 2003 domain controller it says that it has already been run and the forest has been prepared.