Written over the files, or added a lot of new files, they are still somewhere.

First do what someone suggested use Explorer and search for *.jpg and see if you moved them.

If that failes, here's free software that works. I accidentally deleted a whole folder of images, before I backed it up and after I had formatted the card. So the only place was on the hard drive. The less you use the computer before you run this, the better chance that the data is still on the drive.

Basically when you delete a file, it's still there. All that you delete is the table of contents entry that points to the files.

Good Luck! Try this. Free Undelete.

http://www.officerecovery.com/freeundelete/