If it's the same problem that I had with mine a few days ago, i.e. It seemed to be completely dead, the eject button didn't work, wasn't showing in 'My computer' or 'Belarc Advisor'. The only thing left I could think of was a cocktail stick in the manual eject hole (or whatever it's called) and Hey presto!
I had exactly the same problem about a year ago. It has to be the laser. Dvd's have two, one for dvd and one for cd. The fact that it can still read cd's would suggest that the cd laser is still ok. There is no cure I'm afraid. Time to lay it to rest and buy a shiny new one. If you need help installing post back, but its very easy.