When adding a Server 2008 R2 domain controller a 32 bit 2003 server the command “adprep /forestPrep” needs to be run on your 32 bit server. The adprep program comes on your 2008 R2 DVD but when you run this on your old 32 bit server you get an error:
The image file C:\adprep\adprep.exe is valid, but is for a machine type other than the current machine.
This error was obviously from trying to run 64 bit code on a 32 bit machine. What to do? I googled hoping to find a 32 bit adprep I could download and found a number of posts saying to download a 32 bit version of server 2008 and run the adprep program from there. That seemed crazy so I kept searching.
I finally found that I already had a 32 bit version of adprep. The location is cdrom:\support\adprep\adprep32.exe on your Server 2008 DVD!
adprep32 /forestPrep worked like a charm.