Hook the laptop up to an external monitor. There should be a key (likely one of the number keys) that when you press that one + fn key it cycles the video output (usually this is the 5 or 8 key).
If this gets a display then it is a problem with the screen
If this does not work then it is a problem with the rest of the system.
Does they system make any sounds? Have you tried typing in your password and hitting enter if your computer is password protected?