Microsoft recently made a change to the licence agreement saying that a new motherboard is equal to a new computer, hence you need to purchase a new Windows licence.
Here is what Microsoft has to say:
“An upgrade of the motherboard is considered to result in a “new personal computer” to which Microsoft® OEM operating system software cannot be transferred from another computer. If the motherboard is upgraded or replaced for reasons other than a defect, then a new computer has been created and the license of new operating system software is required.”
Microsoft sent a memo to its OEM (i.e. PC vendor) partners asking them to enforce this new policy, every time they upgrade a computer for a client.
More by following the link which references the Education Operating System Licensing Q&A. This would seem to be very bad news for PC “customizers” who invest a lot of effort in upgrading their hardware via piece parts, but there’s an hopeful note in the Q&A:
Can I transfer my operating system license from an old PC to a new one?
ANSWER. Not unless it was purchased as a Full-Packaged Product from a retail store (i.e., Windows in a box). Current OEM licenses for all Microsoft operating system products are not transferable from one machine to another.
So customizers are OK as long as they don’t start with an OEM machine.
The point of all this seems to be that Microsoft is specifically targeting OEM license fraud which isn’t surprising considering recent news. I haven’t upgraded a motherboard in quite a few years, but my assumption is that changing the motherboard changes the hardware “signature” that is created for product activation so that it is readily detectable through the Genuine Microsoft Software (aka Genuine Advantage) program.