says, if you need data recovery software to restore your data, you could try a free hard drive recovery tool
to take a chance. I have ever seen my friend uses it to successfully recover all his inaccessible data back from a corrupted flash drive. So, I recommend it to you and hope it will work perfectly on your drive. Go try it:http://freeware-fix.blogspot.com/2013/02/external-drive-not-detected.html
After completely restoring your data, you could try to format this drive to see whether it could work as before.Note
: You should remember to back up your data on a different drive all the time.