Okay... I went looking online because I had the same problem. I couldn't find anything that was solving my problem. Then I stumbled onto a solution on my own. We have Adobe and I noticed that when I right clicked the drive that came up as my SD card, it gave me some options. That option was "Combine supported files in Acrobat..." So I chose this and a box called "Combine Files" appeared and in the box, low and behold, there were all of my pictures, all 403 of them. I then clicked on "Add Folders" in the upper left drop down, created a folder, and changed it back to "Add Files." Then I clicked on "Combine Files" and the program sent all of the photos into a single pdf file. I then went into the pdf file's File Menu>Export>Image>JPEG>Save As. It then shot all 403 pics out as jpegs. It worked!
Obviousely, this will not work if you don't have Adobe, but I bet you know somebody that does. This will work and it will save your important pics. I hope this helped!