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I bought a "copy" of Windows 7 Ultimate from overseas that turned out to not be genuine.

Without having to reinstall, can I purchase Windows 7 Professional and authorize my current windows 7 Ultimate install? When I enter my new product key, will Windows 7 know it's a Professional key and disable the ultimate features (which I never use)?

I'm looking for a solution that means I don't have to spend the extra money for Windows 7 Ultimate without having to go through a reinstall.

Any help is greatly appreciated.


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Your best bet is to talk to Microsoft directly about this. They'd be interested to know where you bought the non-genuine Windows 7 and could probably tell you more about the process of switching to the genuine Windows 7 Professional. However, downgrading is not possible, you can only upgrade to a better SKU version (in your case there's nothing above Ultimate, so you're out of luck). Either way, contact Microsoft, they're the ones that could probably help you the most. – alex Feb 19 '10 at 7:40
up vote 2 down vote accepted

Officially No - you can't "downgrade" as Ultimate is at the top of the chain.

If you really don't want to clean format there are work arounds, for example:


With the rush to upgrade Windows 7 RC due to it expiring in March 2010, there are some new guides that can help achieve a "downgrade", here is one on Icrontic.

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