I have an Optiplex 760 that originally had Windows Vista. I bought another Dell from a friend that had Windows 7 installed. I used it for a long time, but about a year ago, it was struck by lightning. So I used the installation disk for it, which was Windows 7, to upgrade the Optiplex 760. It worked perfectly, with no problems. About 3 weeks ago, the motherboard failed in the Optiplex. I bought another and installed it and it would not boot. I searched the forum for answers and most were the same, that using a Windows 7 OS on a new motherboard is almost impossible, and it is best to reinstall the OS. I did that last night and it works fine. But now it says my copy of Windows is not genuine and I don't know what to do. I no longer have the original PC that had the Windows 7 OS. I don't even remember what it was. How do I make my copy of Windows 7 genuine? Thank you!!