cd rom is in good working order.. works fine in several other machines

its sharing a channel with a zip drive. when both are wired together the cd doesnt switch on when i boot the pc.(ive tried it as the master and slave)

if i unplug the zip drive and run the cdrom as the only device on the channel it works fine.

ive tried using another crom on the ide channel with the zip and they both worked quite happily.

changed the ide cable and swapped molex connectors.

im at a loss.