Disc inaccessable, can't get to files! HELP!

Hello,

Some time ago I purchased a 500GB portable HD. I needed to make a few PS3 game backups so I divided it into a few partitions which I formatted and changed to FAT32. I left most of the HD memory allocated, only used the 5 partitions I created - 4 with 32GB, 1 with 2GB assigned. Everything worked fine until a while ago, when my most important partition (Uni projects, materials for my thesis, etc.) suddenly became inaccessable! The disc is visible when I go to My Computer, but when I click it, a message appears that I have to format. I really need to recover the files. I've tried Acronis Disc Director, DiscPatch and GetBackData for FAT, but it appears I can't even assign that disc as the one I want to restore files from. I checked the volume properties, it says 0b, but Acronis shows that all the files are still there. If anyone has any idea what to do, please help!