I've got the same problem with an older P4 Dell Dimension 2400. Its a co-worker's old beater that he wants me to resurrect. I did the basic software overhaul as it was full of spyware and viruses and had never been updated. I got everything back to semi-normal except for the exact same problem you mentioned above.
I've swapped them out, tried new cables, nada. I'm wondering if its a mobo issue, bad chipset maybe? I tried installing my own cdroms with the same result. The system recognizes them, they even spin up when a cd is put in, but no data makes it in or out. Device manager says there's a missing or bad driver, but I can't install drivers or firmware from any source. Argh!
Edited by ConserVet, 29 November 2006 - 08:02 PM.