Well if you bought a new charger (which im assuming you made sure was the correct corresponding charger for your laptop) and you replaced the battery (again,assuming you made sure it was the correct battery for your laptop) Have you tried plugging it in to a different outlet in your house?If so...
You may also want to invest in an air duster.They are usually around 8 bucks and it could help you clean out the fans and anywhere dust could be.In your case,if its not fan failure it could just be in need of a good clean.
Bet your glad you bought the computer,seems pretty awesome.More than likely the price of quads will go down once the 3 i7 variations come out this october.I still gotta come over and check it out.As far as the motherboard size im assuming the older it is,the bigger itd be but im sure there are...