I am not sure about data on the external USB drive, because it dead. but the hard drive on your computer might still have the deleted data. (I assume you already delete the data on your computer's hard drive.)
try
Pandora Recovery, I have successfully recovered my deleted data in past with this software and it is free.
according to PendoraRecovery web site :
"How does it work?
When you delete a file on FAT32 or NTFS file system, its content is not erased from disk but only reference to file data in File Allocation Table or Master File Table is marked as deleted. It means that you might be able to recover deleted files, or make it visible for file system again... "