Ed Bott explains how Windows 10’s licensing works. In short, it now ties a Windows 10 license to the hardware and stores it on Microsoft’s servers, so it’s possible to wipe your system and do a reinstall without having to enter the key again. Smart. It even covers most kinds of hardware updates, so upgrading a hard drive shouldn’t affect this tech. But:
The one exception is a motherboard replacement, which will inevitably cause the Software Licensing Management utility to recognize the device as a new PC and require reactivation, typically over the phone. A motherboard upgrade, even if you reuse storage, video, memory, and a case, is considered a new PC. In that case, if the underlying Windows license is from a retail copy, that license can be transferred. If you are upgrading (and not replacing) a motherboard on an OEM PC that was sold with Windows preinstalled, the license agreement prevents the license from being transferred.
That seems like a confusing, unnecessary and an ultimately customer-unfriendly distinction. It’s still licensing by machine, not by person. If the technology exists for storing the license key in the cloud, why not link it to a Microsoft account?