ext. cavalry harddrive does not seem to show up in disk management

okay so my harddrive does not show up in disk management/my computer but does show up in device managers as a simple usb device. I relize it doesnt have a drive letter but since its not in managemnt i cant designate it one. Also the night before we were using it to transfer files for a lan party, the inside seems like nothing is loose, and was working before when i shutdown my ccomp and harddrive, but then i brought my stuff home and it doesnt work now. i need help its veyr frustrating.