Press the Windows Key + S, type in apps and click on Apps & Features. If your file associations are correct, and you want to use the Photos app, let's try to reset it. In our case, you can see that Photos hijacked the JPEG file format, so all we had to do was click and select our favorite app. Scroll down and find JPG or JPEG and click on the Default app associated with that file type and you can choose what program opens it. On the left, you'll see each file type and on the right what program is associated with that file type. If you need to associate one file type, in this case, JPG, once again press the Windows Key + S, type in default app and click on Choose a default app for each type of file. If you've installed a photo viewer that should also show up as an option. Click on Photo Viewer and choose from Photos, Paint, Paint 3D, or Look for an app in the Store. Press the Windows Key + S, type in default and click on Default app settings. Installing or uninstalling an app can break file associations. TIP: Hard to fix Windows Problems? Repair/Restore Missing Windows OS Files Damaged by Malware with a few clicks

Windows photo viewer wont open