@KatManDEW: i have the exact same HD on my Amiga.
Had the exact same issues (look for a thread "problems using OS 3.9 and large drives).
The tool that Thomas suggested didd a fantastic job.
In about 10 seconds, HdToolbox did recongize all partitions, and im now happy and proud owner of a full 80GB on my Amiga!!!!
Use his tool!! You wont regret it!!
Regards
Sebastian