If the camera and all apps can't decode they are usually gone. Try IRFANVIEW too.
No camera I know of allows you to move pictures around like that. So that's a dead end.
However the recurring issue I encounter is that folk don't format the card in the camera. Be sure to do that at least yearly.
When I was downloading some important files from my D70 to the computer, most of them donwloaded fine. About 45 of them did not. These have names with symbols and the jpg extension. For instance DSC_495<.JPG (symbols used are ?><=;:)
All the files show normal file sizes, so I assume the data is there. I can view the file names (not thumbnails or tiles) in windows explorer when I open the card with my card reader, but cannot view images in the camera.
It does not allow me to simply rename the files and change the symbol for a number (Error: The file name you specified is not valid or too long) or even copy the files to a different folder (Error: Could not find this item, It is no longer located in G:\DCIM\850D70. Verify the item's location and try again)
Stellar Phoenix and Picture doctor could not open the file tor eapir it- same error messages. Asoftech recovered other deleted files on the card, but did not open these 45 or so files.
I changed the card reader, no effect. Any suggestions?