For whatever reason, Microsoft opted not to include the Registry keys that enable access to Windows Photo Viewer on Windows 10. Those keys are kept in place if you upgrade from a previous version of Windows, but they aren’t created during the installation of Windows 10. Microsoft really wants you to open all those image files in its new Photos app, instead.

If you navigate to the Default apps pane in Settings, you won’t even see Photo Viewer as an option. The old “Default Programs” Control Panel app isn’t much help, either. Open it up and you can only make Photo Viewer the default association for .tif and .tiff files—not other types of images.

You also can’t simply point image files at a specific .exe file to associate them with Photo Viewer, either. Photo Viewer is actually part of a DLL file named “PhotoViewer.dll” and doesn’t have a separate executable file associated with it.

So, how do you get Photo Viewer back? By firing up our old friend Registry Editor, of course. And after you do that, you can set it as your default photo app.

We’ll need to add the same registry entries that were present on Windows 7 and 8.1, and are still present on systems that upgraded from those old versions of Windows. To make things easy, we’ve put together a Registry hack you can use to make these edits quickly because they’re a little cumbersome to make manually.

Inside, you’ll find two hacks. Run the “Activate Windows Photo Viewer on Windows 10” hack to create the keys and values in the Registry and activate Photo Viewer. And if you ever want to deactivate it, just run the “Deactivate Windows Photo Viewer on Windows 10 (Default)” hack. Of course, there’s no real need to deactivate it in the Registry. You can always leave it available and just associate your image files with a different app.

And remember—this step is only necessary if you’re using a fresh Windows 10 system. If you upgraded from Windows 7 or 8.1, you should be able to go ahead and set Windows Photo Viewer as your default image-viewing application in all the usual ways.

Step Two: Set Windows Photo Viewer as Your Default Image Viewer

To associate an image file with Photo Viewer, right-click any type of image file—for example, a .png, .jpg, .gif, or .bmp file—and select Open With > Choose Another App.

In the “How do you want to open this file?” window, select Windows Photo Viewer. If you don’t see it at first, scroll to the bottom of what’s listed and click the “More apps” option—it’ll show up. Select the “Always use this app to open .___ files” option, and then click “OK.”

If the “Choose Another App” option doesn’t work for some reason, here’s another way you can do it: First, right-click the type of image file you want to change (for example, a PNG, JPEG, GIF, or BMP file) and select “Properties” to open the Properties window. On the General pane, click the “Change” button to the right of “Opens With” and select Windows Photo Viewer.

Windows Photo Viewer will now be the default image viewer for that type of image file. You’ll need to repeat this process for each type of image file you want to use it with. In other words, whenever you open an image that opens in the Photos app, just close the Photos app and use the “Open with” menu to associate that file type with Windows Photo Viewer. You’ll only have to do this the first time you open each new type of image file.