Why isn't my CD drive for my computer working?

My computer's CD drive was working for a while. I downloaded World of Warcraft and some other games on my computer and they worked fine. It has been a while since I have used my CD drive but when I tried to download Spore onto my computer it didn't even read the CD. I checked with some other of my computer disks but they didn't read either. I have two drives for CDs and neither of them work. Any ideas of what might be wrong?