If you want to make other types work as well just replace 'jpegfile' in the code with 'pngfile', 'giffile', 'Paint.Picture' (Paint.Picture is the. reg file and run it: Windows Registry Editor Version will make all JPEG files viewable in Photo Viewer. If that doesn't work, try searching the registry for Windows Photo Viewer and photoviewer.dll to see if there are any references to photoviewer.dll being called directly (without rundll32). Try adding the following to the registry: Windows Registry Editor Version Source) dll instead of rundll32, which of course you can't run directly. dll directly, the entry 'Windows Photo Viewer' still points to the. I think because of your first attempt to run the.