Ok, this can be a tricky question.
Are you swapping with the same model/brand of motherboard, or changing?
Same model/brand:
You should be able to swap the motherboard with little problems.
Changing model/brand:
I personally choose to reformat in that situation, most of the time.
With that said, it is not always necessary.
This biggest issue would be trying to boot into Windows.
You will probably some nasty blue screens, followed by a hard crash.
If you're comfortable updating and swapping drivers in safe mode, then you should be fine.
If you're not comfortable, then I'd suggest the easier route of formatting.