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I'm looking to downgrade the version of windows 7 I have installed on my machine from Ultimate to Professional. I installed from and ISO I got off the MSDN but have just found out that I'm supposed to be using a retail licence on my machine. We've only got retail licences for Professional and I don't want to use and up the MSDN Licenses we have.

Is there a way to do this?

Omar Kooheji
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There is a way. See Downgrade: Change Windows 7 Ultimate to Premium or Professional. I successfully downgraded from an unregistered Ultimate to a registered Professional edition using a universal installation DVD. You edit two registry keys to match the edition you want, then use the DVD to "upgrade", without booting from the DVD.

Here are the two keys to modify:

  • \HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\EditionID: change from Ultimate to Professional or HOMEPREMIUM
  • \HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProductName: change from Windows 7 Ultimate to Windows 7 Professional or Windows 7 HOMEPREMIUM
Jim L.
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No, I guess you can't do that. The installed OS is not the same, it's not just about the key. (Maybe you could use the Upgrade point at install with a Professional disk.)

Apache
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Simply no, you can't (: You must reinstall your OS, to use another Edition.

NB! Microsoft offers to MS Windows 7 Ultimate and MS Windows 7 Professional owners, free downgrade to Windows Vista Ultimate / Business. You can find more about it on Microsoft TechNet if you want.

Anotomix
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