replacing one of those drives with a known good one. That would answer your question in a few minutes.
Kees
I have several machines with CD drives that just sit and blink when a disc is put in. The program/function list does not open, and if you go to the drive in My Computer, right click on it and go to "auto play" (or whatever it is in English -- I work with Japanese machines), none of the options on the list is selectable. The drive won't/can't read the disc.
Should I be looking for a software problem or hardware one?
(5-year old IBM ThinkCentre w/XP Pro SP2)
Thank you.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic