I promptly opened and Command Prompt on the R2 server, navigated to the \support\adprep folder and ran adprep /forestprep. No joy! Now I got the message:
Adprep cannot run on this platform because it is not an Active Directory Domain Controller.So, I went to one of my 2003 domain controllers and ran adprep /forestprep. Another problem!
[Status/Consequence]
Adprep stopped without making any changes.
[User Action]
Run Adprep on a Active Directory Domain Controller.
The image file C:\support\adprep\adprep.exe is valid, but is for a machine type other than the current machine.
It took a few minutes but I finally figured out I need to run adprep32 /forestprep since my 2003 server is 32 bit. Ah, hah! Of course, there's this little message:
Just a little bit more....
From the same 2003 server you'll have to run adprep32 /domainprep as well.
Now that adprep(32) /forestprep and adprep(32) /domainprep were successfull I can promote my 2008 R2 server to DC.
ADPREP WARNING:
Before running adprep, all Windows 2000 Active Directory Domain Controllers in the forest should be upgraded to Windows 2000 Service Pack 4 (SP4) or later.
[User Action]
If ALL your existing Windows 2000 Active Directory Domain Controllers meet this requirement, type C and then press ENTER to continue. Otherwise, type any other key and press ENTER to quit.
Just a little bit more....
From the same 2003 server you'll have to run adprep32 /domainprep as well.
Now that adprep(32) /forestprep and adprep(32) /domainprep were successfull I can promote my 2008 R2 server to DC.