I'm paraphrasing what they have to say
on this page plus what you said, that the mainboard is the tiebreaker item in deciding what constitues a need to re-license OEM software. I really didn't have a clear grasp on the whole thing myself for a long time (heh, I bought OEM Office2kPro from you once upon a time, didn't I ).
Anyhow, I'm sticking with retail-boxed now that I see how this actually is supposed to work. Retail-full-version is licensed to the human being, not the hardware. I doubt MS will freak if people fudge a little on the OEM version, they're probably glad they got their $90 or $140 in the first place, but I'm most comfortable this way myself.
(edited to make more distinction between OEM and retail)