Most likely, it's a mechanical problem caused by the fall. The reading head probably wasn't properly parked when the disk fell so it's probably not properly aligned now. The USB ports are probably just throughput, and weren't affected.
If the disk doesn't spin, then that can be caused by a number of things, from a faulty controller to no power to the disk itself. Are you sure it doesn't spin? When you click on E: in Windows Explorer, put an ear to the box and listen closely.
Most disk manufacturers provide diagnostic software for their products. Did you get a CD with the disk? In that case, install the diagnostic software and follow the instructions. You might have damaged a few sectors, in which case you can probably use the rest.
If you don't have a CD, check with the manufacturer or
follow this link. Good luck.
