I have one of those too, and I am really annoyed with it because it is so finicky. With some DVDs (especially poor quality ones or backup copies of movies), it will read them some days but not on others. Or it will quit part way through.
I recommend throwing it away, and buy a new one. DVD writers have dropped in price by about 60% in the past month, so I bought a BenQ 1620, and I love it.