Help recovering deleted photos

Does anyone have info on whether deleted photos can be recovered? (not from the camera's memory stick, but from the hard drive) My sister had about 200 digital photos she took at an event in Feb. She doesn't think she deleted them but can't find them anywhere-she is a photographer so she has thousands of jpgs on her computer! I suggested she do a search for *.jpg--well, that turned up thousands! Since she doesn't know the original file names or numbers, any suggestions? We have gone to www.webattack.com and downloaded several free programs for recovery- but they are very complicated, so no results yet. Any help would be appreciated- thanks- Jo