If the size of the pictures is correct, try this

Go to the link below, click on Win XP Fixes, click on File Association Fixes, the click on "JPE/JPG/JPEG Association Fix (Restore the default associations for jpe/jpg/jpeg files)" and download the Fix which is a .zip file and open it.

"Extract the REG file to your hard disk and double click it. Answer yes to the import prompt".

JPE/JPG/JPEG Association Fix
http://www.dougknox.com/index.html

But if the size is very small, then you may have lost your pictures.

Some software can restore files in deleted card. You may try it too.
Hopefully it will correct your problem.