External hard drive & idefrag

I used idefrag on an external hard drive formatted as fat32 and now I cannot access any files on it on either a MAC or PC. Does anyone know if doing this corrupted my hard drive?

It seems it may have, yes. There isn't really any need for iDefrag either.
Open disk utility to see if the drive at least shows up.

The drive does show up in disk utility; however, it is not mounted and cannot be mounted. When attempting to repair the drive, we get this:

Verify and Repair disk “C”
** /dev/disk2s1
** Phase 1 - Read FAT
Unable to read FAT (Input/output error)
Error: The underlying task reported failure on exit
1 non HFS volume checked
1 volume could not be repaired because of an error

I suspect the files may still be on the drive, but the file system has been corrupted because when I plugged the drive into a PC, I discovered the drive is being read "raw file system".

Any suggestions on how I might be able to recover the files? I tried testdisk for mac; however, it cannot find the drive.

BTW, I realize now I really don't need to defrag, and especially an external hard drive that just contained data files and pictures!