You could have a dirty laser lense. I have a tip at http://www.fixya.com/support/r4119308-clean_lense_cd_or_dvd_player
which will walk you through the process.
If this does not solve your problem I would try reinstalling the driver for the CD ROM. The driver should be on the disks which came with the computer. The process is basically insert the disc and follow the instructions to reinstall the driver for the CD ROM. This may require a restart of the computer.
In the unfortunate case where neither of the two suggestions work, you will have to install a new CD ROM. They are not that expensive anymore. In fact you may want to upgrade to a DVD/CD burner. There are many sites to get them from. I like to use http://www.newegg.com
. They are easy to work with, have good prices and an excellent return policy.
Thanks for using FixYa and for the generous rating!!