This all depends on the kind of damage it has sustained.I have a problem with my external hard drive, when i plug it in my laptop.. it takes too long to acknowledge it and when i open a file it would hung, i tried to reformat my external hard drive but it says reformat unsuccessful..
After a recent critical crash, I made sure to have multiple media for recording backups. I was able to recover most of the data using Partition Recovery, but I was very nervous about this task.The typical, or designed, use for an external hard drive is for it to serve as a backup drive or a transport drive. Should such an external hard drive become corrupted, its contents would be erased by cleaning it with the Diskpart command. This would be followed by re-initalizing the external hard drive using an app such as Disk Management and formatting it as new. As a backup drive, the drive is restored from a restore/recovery auxiliary drive/disc or from the source files on the computer. If the drive cannot be fixed, it is discarded.
On the other hand, if this external hard drive is used as the main data drive and these files need to be recovered, then the best route to repair it would be through a professional hard drive recovery company. There is nothing available for the user to fix a corrupted external hard drive and an amateurish attempt at doing so by downloading software apps off the Internet is foolhardy.
It is bad practice not to have the source data files along with a backup set. The best practice of safeguarding important files is to have the source along with two backup sets, the two backups on different media or storage sites.