I recently bought a whole bunch of used CDs and I'm trying to rip them. I've done about 100 and have about 250 to go. Most have been fine, but one CD made a clicking sound like a bike with baseball cards in the spokes. The disc looks normal to me, but I tried it twice and it did the same, so I ejected it ASAP and didn't rip that disk. Another disk made a different noise, it was slightly dirty so I cleaned it and now it's fine. These noises have me worried though. Am I going to wear out my drive by ripping all of these? Are there any statistics on how many CDs a drive can read (or write, not that I do that much) before failing?