Change Windows 7 Edition after install

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?

Answer

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