Son's memory card threw a wobbly and all his coursework pics disappeared. Not visible on any PC or in camera. Tried a few programmes I already had for recovering data, but no joy. Searched the net and found a freebie called PhotoRec 6.11 from www'cgsecurity.org which found and restored over a thousand pictures, basically every picture he had taken and deleted since he started using the card. Just a heads-up in case anyone else has a similar problem.