You say that the battery discharges quickly sometimes and sometimes it doesn't regardless of your actual percentage. You say that the power converter is heating up, but also sometimes keeps cool. Obviously, sometimes your hardware is causing a large load. The power converter has a thermal shutdown and the battery will die excessively fast if too much power is drawn. This time start eliminating the problems by taking hardware away from the computer. Remove the CD drive bay and see if this helps. Remove other parts of hardware until the problem goes away. Do a heat check on the computer to see where the power is being most dissipated (whats getting the hottest). The part that heats up the most is most likely the culprit (the battery will heat as power is consumed).