Published at LXer:
"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." Please note that this does not go for retail copies of Windows, but only for OEM versions.