|How did you determine the motherboard was the problem? Did you buy a decent replacement board or the exact same one?|
eMachines are notorious for using crappy Bestec power supplies. That was very likely the problem. Also, you should ALWAYS benchtest a new board BEFORE you install it in a case. Have you done these sorts of repairs before? Did you re-mount the heatsink properly on the CPU? Off with the old thermal paste & apply a dab of fresh paste?