"...an HDD is pretty much an HDD..."
Not so. It may not be an IDE drive at all.
If the drive is REALLY old it may have a ST-506/ST-412 interface. Possibly also ESDI or SCSI (less likely).
ST-506/ST-412 drives can be recognised by having two ribbon cables (instead of the single cable used by IDE/ATA and SCSI). One of the cables is 20 pins wide and carries data, and the other is 34 pins and carries control signals.
If you want to read it you'll have to find a working mobo with an ISA/AT bus and an ST-506/ST-412 controller and set it all up. Best contact your local computer interest group and see if any of the old guys like me still have some of the kit around.
See
http://www.storagereview.com/guide20...d/if/obso.html
Good luck!