Take the bulb out of the projector. Hold it up to a light. There should be little "arms" sticking up in the air. There are usually three or four of them. At the end of the "arms" there should be a fine piece of filament connecting the three or four arms. If there is no filiament, your bulb is useless, and you should purchase a new one. If the filament is there, then you might have a problem with the projector. Good luck.