If you change the motherboard then windows will deactivate itself and you will have to reactivate it. It probably won't work to do it online so you'll have to do it over the phone. Sometimes you can just use the automated system but just make sure to tell it that you've only ever had it on one computer. I told it that I had a family pack license on 3 computers (which is allowed) but it refused to activate me because it assumed I was violating the license. If you can't do it with the automated part then you can talk to a person and tell them that you had to change out an old motherboard. They've always been able to reactivate it for me.

As for AMD boards I'm not really sure so hopefully someone else can answer that part.