|If you have not dropped the drive or otherwise damaged it, your problem was probably caused by you NOT clicking on the Safely Remove Hardware icon in your Taskbar and STOPping accessing the drive BEFORE you unplugged the drive while Windows was running.|
There are several programs that you could try that will probably fix your problem.
Specifically, links to some programs that can repair the data damage are here -
see response 2:
You may need to plug it into a different USB port.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1: