That was the problem that my Compaq had, they changed the motherboard and then they changed the power board. Sometimes it also has to do with the battery... like my brother's laptop he can only keep it plugged in for awhile and then he has to unplug it because if he leaves it plugged in, it shuts off. So he's just sitting in the computer lab, plugging and unplugging his laptop, people were looking at him like he was crazy.