When the system starts, or when I put a CD in, the green lights on all of them blink for a while, and then just stop, so somehing "is" happening.
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Your connectors might be halfway making contact. Are both CD players on the same "ribbon" that connects to the motherboard. If so, the connection to the motherboard might be iffy, and needed to unplugged and plugged back in a few times to rub off oxidation.
I realize you won't know unless you open up your computer.
This is a really dumb question, I know, but woudl Dell have sent me a motherboard schematic?