Bug fix of a tiny MFC application

I have a very simple, tiny demo app which does the following: Opens a small program window with 1 checkbox. The app allows the user to select which viewer will open image files with the extension [.jpeg]. It should not affect images with other file extensions, including those with [.jpg]. Note: it needs to override the annoying tendency of Windows to open such files with the "Windows Picture and Fax Viewer". Checking the box will turn this on, and unchecking will return things to where they were before use of the demo app. Currently the code does not work on some computers. Your job will be to fix it to work always. Please note: this job requires that the desired results work on most computers, not simply the coder's own computer. I may need to verify the results with some testers to make sure it's working correctly. Thank you for reading my bid request.