Admittedly, this is a bad situation, but not hopeless. As it was told above, when files get deleted, the data does not immediately get erased from the disk; it gets marked as free space for new data. If the disk has not been heavily used since the files disappeared, there is a pretty good chance of recovering them.
Try some self-recovery with free tools like Recuva or KickAss Undelete.
These often work quite nicely for simpler cases or files that were deleted recently. You can also go for paid options like EaseUS Data Recovery Wizard and Disk Drill, which offer added features to support more complex recovery scenarios.
However, it has to be said that no software, whether free or paid, can guarantee success should the data have been overwritten or corrupted over time.
If those tools don't help-which is quite possible to happen after such a long period of time-then probably one of the most reliable options can be professional data recovery services. This is because such companies use very special equipment and advanced techniques even to recover files in very awkward situations. I have heard good things said about Salvagedata. Avoid the disk entirely until you have identified your course of action, as writing new data can overwrite old files and render recovery impossible.
