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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?

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the answer you accepted is not true. Could you please change the accepted answer? – Jim L. Sep 3 '14 at 14:15
@JimL. your answer appears to be accepted now and works. – davenpcj Jun 29 '15 at 23:32
up vote 2 down vote accepted

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
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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.)

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Not true. See my answer. – Jim L. Aug 21 '14 at 2:08
@Jim L.: what answer? Where? – Shiki Aug 22 '14 at 6:05
Someone keeps deleting my answer because it does not duplicate the linked content. I can't believe someone thinks it's better to have no answer than an answer that references instructions. :-/ – Jim L. Aug 30 '14 at 17:11
I've changed the accepted answer. – Omar Kooheji Sep 3 '14 at 14:16
@JimL No problem, gotta make sure the truth is out there. – Omar Kooheji Sep 3 '14 at 14:19

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.

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Not true. See my answer. – Jim L. Aug 21 '14 at 2:07

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