Short answer: Yes.
Longer answer: if the key was registered to that motherboard (if you got that far) it may or may not fail validation as "already used." I would guess not, since other hardware is considered in detecting if the key is being double-used. If that happens, you can call Microsoft and explain and they will activate it.
Are there hardware problems that we could help you resolve? Unless it was all due to a bad mobo, perhaps we can help you get to the point where it at least gets to BIOS every time.