Hi Alison3 and welcome to CD Freaks
It could either be that the CD lens of the drive is dirty, or that it's dead. If it's not a slot-loading drive then you could look and see whether there's any muck on the lens, or give it a blast with some canned air. Unfortunately if the lens is dead, then you'll have to replace the whole drive even though the DVD lens is still apparently working.
How old is the laptop?