Tried connecting it to a macintosh (OS X based) system?
Think you could take the drive out of the external container it is in and put it in another, connect it to an adapter or install it inside a computer?
Ever used a program called "testdisk"? It could help you see what the current partition schema is on the system and try to recover things - especially if you know how it was partitioned/formatted before (one or multiple partitions, FAT32, ExFAT, NTFS, etc.)
How 'old' is the drive in question?
Using the same cables that came with it? Have you tried other cables?