External hard drive no longer recognized as NTFS

"I've had good results with GetDataBack. It claims to support scenarios like yours, but honestly I've never needed it for that. It's not cheap ($80), but does provide a trial version that you can use to see how well it will recover your files.

Note that depending on the state of the drive, any file recovery software may have trouble recovering filenames. This is just because of how the filesystem works and what damage (if any) it may have sustained."