Memory After turning on my S500 after changing the batteries the screen flashed on and off a few times with and its seem to have changed where the pictures save to on my camera. It lost all the pictures i previously had on there and is now only allowing me to take about 20 pictures. Please help!

Sounds like the camera changed the name of the recording folder. My Sony does that sometimes with video and still frame shots, its puts them in two different folders. It also may be only recording onto the internal memory. Take the memory card out and try to use a card reader and see if there is anything on it. You can use various recovery software to check it out if you dont see anything. pics are never lost, they are simply not indexed anymore. When you delete pics, you are basically resetting the table of contents of the card. It will now allow new pics to overwrite the old ones. Same as a hard drive. If you truly want to wipe a card or hard drive, you need to overwrite the entire media with 0's and then 1's at least 5 times over. That is minimum when erasing govt. data. So the DATA is still on there, its just not indexed. recovery software will find and rebuild the index table.

Dear Claireee,
If this is DSC-S500 Sony cyber-shot, you should scan it with updated anti-viruse software and then format its internal memory with USB connected to PC. Hope problem will be solved.