The CD/DVD, as well as the hard drive head, are one of the few remaining electro-mechanical parts of any computer system. The placement of those heads is really quite critical and the least amount of dust in the mechanism can ruin them. Of course, most HDs are hermetically sealed and that keeps the dust out, but makes it harder to keep them cool. These removable writer/readers are dust collectors. Well designed ones will do a better job of preventing disaster, but they usually don't last as long as the HD mechanisms, even though their positioning is less critical. I've had and heard mixed reports on the effectiveness of cleaner disks, but they are worth a try if the drive is already broken, IMHO. But they won't fix much except knocking off some dust bunnies. And if those critters aren't removed for stew or rendering, they can still cause trouble! I think some species of gremlins actually live off them!
If the thing simply can't/won't read CDs but works with DVDs, and there are actually two different lasers being used, there may not be much hope for the CD portion. And I'm not sure I'd trust the DVD portion for any writing, a burned DVD may or may not be readable by any other drive.
