Hi and welcome to the forum
Do you have this problem with [I]every[/I] CD or only with [I]burned[/I] CDs? If the drive is not able to read both pressed and burned CDs, then the CD laser is damaged.
Burners have two separate lasers, one for CDs and another for DVDs. If only the CD laser is damaged, you can still use that drive for DVD. The only solution for CDs, however, is to buy a new drive.
If you have problems only with burned CDs, then the most probable culprit is the CD. Burned discs can become unreadable after some time (related on the disc quality and on the way the disc is stored).
Another possibility is that the optical pickup is dirty (dust can go everywhere:doh:), so it is sufficient to clean the drive to solve