Hi Manualfax,
It sounds like your question is regarding Product Activation and not Windows Genuine Advantage related. Although your question is out of scope for the support here, I think I can answer your question.
If I understand correctly, you think you will have to reactivate your Windows after changing out your Motherboard, that is correct. (Changing out any other hardware may or may not trigger a reactivation scenario, depending on which and how may components are changed, but Motherboard changes are an automatic reactivation).
If I understand correctly, you are asking if you will BE ABLE to reactivate your Windows after the change. As long as you are using Genuine Windows Software and a Genuine Product Key (that belongs to you) I, of course, can not make any Guarantees, as I do not know all the details, but I don't foresee any problems.
Note: You may not, however, be able to reactivate over the internet and will be required to use the Active by Phone method (takes a few mins longer, is all) and just explain, to the Activation Agent, that you did a hardware upgrade.
If you are, in fact, asking about Validating the Genuine status of your Windows install using WGA, then, again, as long as you are using Genuine Windows Software and a Genuine Product Key (that belongs to you) I, of course, can not make any Guarantees, as I do not know all the details, but I don't foresee any problems.
Hope that helps,
Darin Smith
