Hello, I wanted to upgrade my main computer to windows 8 by buying it and installing it. But I want to use the windows 7 copy that is currently installed on my main computer on my secondary computer that is still on vista. I know how to find the product key which I have, but I don't have an actual physical disc copy of windows 7 so how will I install windows 7 without a disc with the product key I have? So Pretty much I guess I have to get windows home premium ISO file and type in my product key. But I want to be sure I get this file legally. It means nothing without the product key anyway.