You have this under the home theater forum. Are you trying to play a video on the phone? Or get the phone to show anything on the screen? If you are trying to play a video it's probably encoded in a way that your phone doesn't understand. If you are using the default program that came with your phone I suggest getting something that handles more formats like VLC.
If you are trying to get anything to show on your phone, I'm guessing the screen itself is dead. This is likely if it's been dropped recently.