Hp laptop with black screen?

when you turn on the computer the screen stays black. When you hook it up to an external monitor there is no image. all the lights on the computer come on. and also the small lights next to the caps lock on and the scroll/num lock on are blinking.I talked to HP and they had me go through the protocal; remove battery take out ram..etc. It didnt work. Does anyone know how to fix this issue?