It depends entirely upon what specific type of OEM re-installation CD you
have. While there's nothing in the OEM EULA to prohibit upgrading the
motherboard, you may have a technical problem.
If you have an unbranded, generic OEM installation CD, you'll have no
problem. However, if all you have is a branded OEM recovery CD, or a
BIOS-locked, branded CD, it most likely won't work on the new motherboard.
Some OEMs went a bit overboard when implementing Microsoft's anti-piracy
wishes.
I had that problem with a Dell box. They replaced the motherboard. Turns
out, that was unnecessary ... the problem was a bad memory module!
But anyway, after reinstalling Windows using the Dell recovery disk, Windows
asked for activation. The BIOS of the replacement motherboard does not have
a Dell service code in it. So Windows won't activate. (Why didn't the idiot
repairman deal with this!?)
I called Dell and they said I could download a small program that would
update the BIOS to fix the problem. Unfortunately, that program failed,
saying that it only works with version X of BIOS, and I had version X minus
1.
I called Dell again, and they had to work through an entirely different
solution. Can't remember the details. But this is a pain you don't want to
go through!