IDE devices are easy.
Primary Master == hda
Primary Slave == hdb
Secondary Master == hdc
Secondary Slave == hdd
If you throw another IDE controller in the box, you'll get hde hdf and so forth.
I *believe* SCSI devices work much the same.
sd0 == first scsi device
sd1 == second scsi device
(though SCSI ID might set it's "sd" number too)
Zip drives via the Parallel port are probably still considered SCSI devices, so that would explain it sitting on sd1
If you run "dmesg | grep hd" you'll see the bootup messages for the IDE bus, might get you going in the right direction.
Don't just start mounting stuff in /dev. /dev is a wasteland