Thanks so much for the suggestion. It still doesn't work, though, unfortunately.

Oddly enough, Mandrake 9 will find the CDROM after loading the ide-cs module (and supporting modules). I rebuilt the initrd filesystem and added those modules (pcmcia_core, yenta_socket, ds, ide-cs), but it still doesn't work. I suppose I could spend a lot of time figuring out how Mandrake is booting, and then re-build the Knoppix kernel and boot method, but it's a bit beyond me and I am out of time and am giving up on this for now.