How should I try to repair corrupted data?

I had a folder with all my music in it and now it’s scrambled. Initially it showed me some of the original folders along with folders and files that weren’t supposed to be there. Completely random names and extensions, with some characters I’ve never seen before. So I decided to let windows check the external drive for errors (it’s always offering to). What has happened is that the folders which remained have also been replaced with unreadable data and I seem to have lost about 200GB in total. I can’t imagine how this happened but I’d appreciate any advice or comment.

(Looking at the behaviour of the disk it seems like the folders broke rather than the files but I really wouldn’t know)

EDIT: Windows 7, WD Elements 1TB