Just a quick word of caution when servicing laser devices like CD drives while the power is on (i.e. to see when the drive head moves, etc.):
The laser is invisible and can cause eye damage if you look into it (which is something you can do if you take off the top cover of the drive and expose the lens.
I really don't know how much damage a DVD or CD laser could do, but I've seen drives with safey warnings on them. Normally, I believe that technicians who service these use special glasses as a safety precaution. I guess you could just make sure you're not peeking into the lens while the drive is powered up.
