Using Free Windows 10 License on changing Hardware If you buy a new copy of Windows 10 you have a product key. In this case, the product key can be used to activate Windows. But there’s no product key if you’ve upgraded for free. When you perform an upgrade from within Windows 7 Service Pack 1 or Windows 8.1, the upgrade process registers a unique ID associated with your PC’s hardware on Microsoft’s Windows activation servers. In the future, whenever you install Windows 10 on that same PC, it will automatically report to Microsoft’s activation servers. Microsoft will confirm that the PC with that specific hardware configuration is allowed to use Windows 10, and it’ll automatically be activated. If you just replace your hard drive or upgrading your graphics card, it shouldn’t cause a problem. If you’ve just changed a few peripherals, Windows 10 may just automatically activate itself after you clean-install it. However, replacing your computer’s motherboard or CPU will likely pr...