Try connecting to an external monitor, if you do not have one see if you can borrow a friend's monitor for testing. If the external monitor can display an image then the problem is with the laptop display, if the external monitor does not display then it is the system board.
Power issues tend to be the system board. If you can open the case and remove all of the RAM and then turn it on, you should get a beep error. If you get a beep error in this case, it means the processor is working. If you are getting an beep error when trying to boot note the sequence, it is usually a pattern of long and short beeps and repeats the pattern.