Hi,
I can tell you that you are lacky man that even starts in safe mode when you change some new parts especially MB your windows can't even boot in safe mode.So I'm telling you if you are having some personal files move them in other partition and install a new windows.
i second this, u are indeed luck, any h/w change of that nature does require a fresh install. but u should be able to do a new install and keep all you programs.