Let's get one thing straight - this is a combo unit, not a DVD writer, am I right?
If the upper sentence is true, then we move on...
If it's old, it is possible that the dust that gathered inside doesn't allow dvds to be read correctly but cds are read - this is possible because they read different laser beam intensity to be read, also data tracks are wider.
If it's new, and previously it read dvds, then you could look for the problem not into your drive, but your dvds.
You shouldn't bother about the drivers, removing the drive from device manager and such, because if it reads cds, then the software problem is out of the picture, in my opinion.
This is it for now. Let us know about your progress!