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I have a retail Windows 7 Home Premium license and installation CDs. I'd like to do a fresh install of Windows 10 on an old PC that's currently running Windows 10. If I wipe the machine and reinstall from scratch, will I be able to install Windows 10 and activate with my Windows 7 license, or can I somehow get my activation key out of my existing Wicked 10 installation? Or is it better to just use "Reset this PC"?