It does sound like the drive itself, but at the very least try the hard drive by itself in a computer or with another external case.
It would be best to rule out the computer too.
1) Hook up external case to another PC (if NO, then...
2) Insert hard drive as a second drive OR use another USB case, (if no, then...
3) freeze? (never heard about this, but you ARE desperate at this point. The odds of anything working are low as your electronics are fried on the hard drive)
4) RMA (return to Manufacturer)