If the system cannot find the SCSI PCI card, then your problem lies there. I have a SCSI-50 card that was in my MDD when I bought it (It's branded for use on a Mac) and in Leopard system profiler, the card shows up, but there is no driver for it. I'm not sure if SCSI support was dropped in Leopard (Or an older OS) but perhaps using an older version of OS X, or Linux will make the drive show up.