Windows 7: "Win 7 Pro cannot upgrade to Win 7 Pro" Issue when repairing Windows

I am trying to perform a repair install according to the excellent guide in this forum, however after accepting the Terms and Conditions, This pops up:

Windows 7 Professional cannot be upgraded to Windows 7 Professional. You can choose to install a new copy of Windows 7 Professional instead, but this is different from an upgrade, and does not keep your files, settings, and programs. You’ll need to reinstall any programs using the original installation discs or files. To save your files before installing Windows, back them up to an external location such as a CD, DVD, or external hard drive. To install a new copy of Windows 7 Professional, click the Back button in the upper left-hand corner, and select “Custom (advanced)”.

What can I do?

It's an unusual message. If you have a pre-SP1 installer did you uninstall Windows 7 Service Pack 1 (SP1) to make them match?

Is it possible one is 64 bit and the other 32 bit?

I'd find another Windows 7 Pro installer of the same SP status to try again, especially if I have SP1. You can google Official Windows 7 ISO downloads at My Digital Life to find one to burn to DVD using Windows Image Burner.

You were right! I downloaded a proper, official unmodded ISO from My digital life and it's installing right now! It's non-SP1 btw. Hope it works and thanks for the tip... I was about to give up and do a clean install...

You may still need to do the Clean Reinstall since Repair cannot always winnow out bad settings. But not to worry - it is always a superior install, solving problems and giving a fresh start. Follow these steps to get a Perfect Reinstall

Hey all - I downloaded the ISO from above and am still getting the "Cannot upgrade from Pro to Pro" message. Any other suggestions? (yes, SP1 is removed.)

Try it again. Repair Install

If this fails clean reinstall: Reinstalling Windows 7