DVD R/RW Drive only reads DVD’s and not CD’s

Hi,
I have been having a problem with my Dell Optiplex 360 DVD drives. Whenever I insert a DVD it plays fine but it always fails to read any CD. I know it is not a problem with the CD's as they work fine on my laptop. I have even tried XP recovery CD's and these don't work either. The CD's just don't get recognized. Please help me solve this.
Ameet
