Um, this might be a repeat - but I didn't see my previoius response posted:
The machine has been running win95 successfully (if you call that success) so the hardware is fine. The SCSI adapter has its own BIOS; I'll double check the settings in there but I don't remember anything that would matter there.
The error I see is just after "Red Hat/Adaptec aacraiddriver 1.1.2": "kmod: failed to exec /sbin/modprobe -s -k scsi_hostadapter", which repeats a fdisk /total of 3 times. When I try to run fdisk (or cfdisk) I get 'unable to open' whatever I try there (/dev/scd0, /dev/scd1, /dev/sda etc.).
I will try removing the sound card, while I'm in there I'll change one of the HD's so its SCSI ID=0, and I'll remove the existing DOS partitions with DOS FDISK. We'll see.