Posted 13 October 2013 - 09:16 AM
The most common cause I come across is overuse (for want of a better word), the units have 2 lenses, one for CD's and one for DVD's, which is why you often see only one format working as in this case, and my first question is do you use that format a lot, and how clean are the disks you put in it, and if it comes back as heavy use, and probably some disks not as clean as others (you may not always see the dirt the lens could pick up), then it's pretty much a dirty lens every time, and by that time a lens cleaner probably wont be enough, it's good practice to use a disk cleaner say once a month, and wipe each disk as you put it in the unit, it will extend the life of it by doing this so you know for the future.
So pretty much as paws said, it will need replacing as it is faulty, good news is they are pretty cheap these days, and easy to swap usually, just make sure you know if it's a Sata drive or ide, you should easily find that out by google'ing the model number, often on the front of the drive, as you will want to get the same format when replacing it as you can use the existing cables to make it easier, but checking the filters as paws has said costs nothing, so is always worth trying first, but I thought adding about dirty lenses etc. may also help as well as paws advice.