I will have to agree with some people here, it could be the RAM. When my celeron PC had the RAM not seated properly, it would not even boot up. It worked beforehand great, then, after the RAM was seated properly, booted right up no prob.
Oh, yeah, smoke is not good, you could have done more damage than you think.
Anyways, just TRY the RAM, get a cheap baby stick of 256 and try it out, just to make sure. It will not hurt to try, and it will rule out a very possible cause.