I am not sure what I have done to one of my laptops but I can not longer open any pictures in the Windows Picture Viewer file. When I try I get a message that says:
"Adobe Reader could not open 12432142134234123412.jpg because it is either not a supported file type or because the file has been damaged"
I think I know what I did but now I don't know how to undo what I did

I changed a setting while I was trying to scan something that needed to be sent as a PDF file. I'm positive it a setting for my Windows Picture views. Can anyone help me figure out where I was that I changed the set. I am so ticked off that I managed to do this and now don't know how to undo what I did.