Disappearing files in EP?

Wonder if anyone could help. I have a load of folders with different pics/ vidoes/ media etc in them. Turned on my pc today and most of them are empty, well not exactly empty. I open the folder and can see nothing at all but the folders are still taking up memory, so it's as if my data has become invisible for no reason. Any advice?

P.S. Have tried burning one of these empty folders to cd and tried it on another computer. It didnt work, just a couple of folders saying Thumbs.db and Thumbs.db/ dncryptable/ $data showed up. (The other system is a mac). What you think? Would be very grateful!