This is purely a licensing issue with Microsoft.
Apparently, the Microsoft OEM license agreement says:
“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.”
if you have your own upgrade or full retail version of windows then do a new install after you've installed the motherboard.
If you decide to go ahead with this motherboard replacement without re-installing windows, please remove all chipset drivers, storage drivers, sound drivers, display drivers BEFORE changing the motherboards.
I've done this previously: Used my laptop HDD in a PC and it worked perfectly. Was with windows 8 though...