Presumably you have data on here that is not backed up. If that is the case, here's what I would do:
Use WinHex or R-Studio or DD or similar application to make a bit-for-bit image of your drive to another blank hard drive. This will prevent you from making any mistakes in the recovery that can't be undone.
Use R-studio to scan the drive looking for files. Depending on how bad the file system damage is, you can likely get back the files but might lose the names of the files. Recover this information onto a 3rd blank drive. Or at least a 3rd drive with plenty of free space.
If you don't know why the file table is messed up, assume that the drive is about to physically fail. Make an image. It might end up being unnecessary, but an ounce of prevention is worth... something. I forget the saying. Just do it