Unfortunately then, it does sound like a dead drive.....if it really won't work with another PC, then the only last-ditch suggestion I'd have would be to pop into PC World and enquire whether they have a service that's worth trying. They do various repairs and restores, and they're mostly not bad value - but it depends what you paid for the drive and whether there's anything on there that's irreplaceable to you.
If you can get a diagnostic report that says it's a manufacturing defect, say a bad sector or something, then even if you've had it longer than the warranty, you're entitled to argue that it was not fit for purpose when sold to you...... you might get a replacement.