There could be many reasons for this, but you need to give us more information. The cd could be dirty. I've seen small specks and smudges render the cds useless. I would as a first course of action recommend that you clean the disc with a damp lint free cloth rubbing from the center hole out to the edge in straight strokes. Do NOT rub around the circumference of the disc! If that doesn't do it, look for scratches and imperfections in the surface of the disc. If the disc looks clean and sound, we'll need to try another course of action.