And, yes, you must do a clean install, as it is not possible to do an "in-place" upgrade between architectures.
I just bought 3 Optiplex 790 desktops from the dell outlet.  2 of them shipped with Win 7 Pro/64, 1 with Win 7 Pro/32.  I haven't powered any of them on yet. I would like to run Win 7 Pro/64 on all of them.  I was hoping since i haven't accepted the EULA yet i may be able to switch it.  I figured i could use the Media from 1 system to re-install if there aren't any legal ramifications. Is re-installing the best technical solution, and is it acceptable per the license agreement?  I don't want to purchase ANOTHER Windows 7 license.
Windows 7 32/64 bit question