Switching from AMD to Intel

Windows generally requires another activation once the motherboard is swapped.

It sees it as a new computer. When my old XP rig dies and I tried to transfer the HDD with the OS, windows demanded a new product key.

After an hour on the phone with windows support, they gave me a new key.

Your mileage may vary.

You will need to re-install Windows. The driver set in your existing installation will likely not make it past the initial loading screen. Then, as Z1Only points out, Windows will see it as a new PC and demand to be activated again. If it was a Retail version, it may succeed, but if OEM, it won't. I too have explained the death of a motherboard to Microsquishy, and been allowed to reactivate an existing copy. Chances are, their system indicated that I'd bought numerous copies of Windows over the years, and was therefor not likely to be a pirate. I cannot speak to the results you will get, but I think I'd be optimistic.