Have you made sure that there is absolutely NO video? Try taking the computer into a very dark room and check if you can see what you'd expect to see, but very, very dimly. A common part that goes out in some laptops is called the FL Inverter Board, which handles the video signal translation between the LCD panel itself and the video card. When it goes out, all video turns EXTREMELY dim and hard to see. It tends to cost about $50 for a new one and is very easy to replace.