It sounds like the file table is corrupt. It maybe that you data are still intact but the index windows uses to locate them isn't.
R-Studio (from r-tt.com) makes a good job of recovering from such loss.
They have a number of options for software, some cheap, some not so cheap.
If you want to risk losing it all over just a few dollars for software then you could try Testdisk / Photorec from christophe grenier. It's a powerful tool but manual.
If you have no experience with file table work, then you run the risk of making things worse.
And what is R-studio? Do you suggest any program?
R-Studio is a data recovery program. I suggest it because it is capable of doing the job.
If you want a long list of free "get lucky" programs, then fee free to try google.
You could spend hours installing and uninstalling and removing all sorts of crapware they put on your machine.
You may then realise some aren't that good and not actually free, but want your money too.
That's it, good luck.
Kern