|A couple of long shots:|
Firstly, copy them to some other folder to see if they are the same when double clicked from there.
Secondly, I have sometimes found that damaged pictures will open in IrfanView if nothing else. It is a good free viewer but if you don't want to keep it just download and install it to see if it gives the same bad results. You don't need to associate files with it just to try - open the viewer and find them from there. If it views any of them properly then get it to save them again.
I don't know the reason for the damage and can only imagine there was some Windows giitch that shot through the system and messed them up. It's unusual but a pain if it happens.
Always pop back and let us know the outcome - thanks