I have an Inspiron 1501. When I plug in the power cord the screen gets extremely dark. When it is running on battery, the screen is bright and good. Seems like it is the opposite of what it should be! Is there a way to fix this so that I can actually see what I am doing!?!?
Check the power management settings in the BIOS setup (F2 at powerup). If there's nothing there indicating a dimmer screen on AC power, then you've got a mainobard problem.