Hi Forum ! I have downloaded the OEM version of Windows off the internet. I know for a fact its the OEM version because the manufacturer's code told me its an OEM version as I googled that code up. Now, I didn't activate the OEM version because I don't have a product key. So, I purchased my Retail version of Microsoft Windows 7 Professional from Amazon. Now for my question: The Retail version of the Windows I have purchased will come with a Retail product key. Can I use that Retail product key to activate my OEM copy of windows that I have installed on my system ? Or do I have to do a complete format and full installation off the Retail DVD that will come with it ?