[sfilipov]

They went a step further. Once a Windows 10 machine is activated, a "hash" of its hardware is taken and associated with the product key. When you reinstall Windows 10, the activation service matches your hardware information with the product key. You need to enter a product key only the first time you install Windows 10 on a particular machine.

[Already__Taken]

When I was building machines and asked about the OEM licence, this hardware hash is related to the motherboard. MS consider a new motherboard a new PC, everything else you should get away with changing.