Thanks for the information in the mailbox. However, even that program could not recognize the JPG files.
The USB was formatted when the program downloaded the booting files on it. The program was not what you mentioned.
Recuva said that the unviewable files on the memory card were overwritten by newer pictures that I took. It is strange that the pictures were overwritten in descending order, yet the oldest, the viewable ones, were not the first ones that I had ever taken with a camera with that memory card in it.
It seems that I can not recover the overwritten files on the memory card. The last hope is that I can recover the images from the USB, which was completely formatted.