A:Answer Since most Windows based computers come with Windows installed, if you want to replace it with this retail product (and I can only think of a few unusual reasons why you would want to do that), you will have to buy a retail version per computer. Mostly people buy this if they build their own PC which doesn't come with Windows. If you had Windows 10 and it won't let you upgrade, buying this won't help you because the computer hardware itself isn't able to run the newer version.
