just to clarify-you can reach an A prompt, change to a prompt for your cdrom, but hitting dir brings up an error?
if I have that wrong, my advice would be to get to that situation. try an option of booting with cdrom support, but not installing windows immediately.
once you are at a prompt for your cd, try a dir. if the same problem occurs, try reading the cd on another system, or try reading another cd.
also, any errors noticable during bootup? messages about the mscdex.exe, etc?