How to Repair an External USB Hard Drive
External USB hard drives are normal hard drives that attach to your computer with a USB cable. As normal hard drives, they are subject to the same types of problems as internal hard drives, namely developing bad sectors due to errors when the operating system reads data from the drive or writes data to the drive. These bad sectors should be repaired to keep the USB hard drive functioning properly.
Attach your USB hard drive to your computer with a USB cable and wait for the operating system to recognize the drive.
Open the Start Menu and click on the "All Programs" button.
Click on "Accessories" and then click on "Command Prompt."
Run the disk checking command with the "repair" option by typing "chkdsk x:/r" into the command prompt window. Note that you should type in the drive letter of your USB hard drive instead of the drive letter "x," unless "x" is the drive letter of your USB hard drive.
Press "Enter" to execute the "chkdsk" command, which scans and repairs your hard drive.