After you do that, you can then set it as your default photo viewer. It’s just hidden, and you’ll have to make a couple of Registry edits to have it show up. The interesting thing is that Photo Viewer is still there. However, if you perform a clean installation of Windows 10 - or buy a PC with Windows 10 already on it - you can’t access Photo Viewer at all. If you upgrade a PC running Windows 7 or 8.1 to Windows 10, Windows Photo Viewer will be available, and you can set it as your default photo viewer if you want. RELATED: How to do a Clean Install of Windows 10 the Easy Way You can get Photo Viewer back in Windows 10, though. Windows 10 uses the new Photos app as your default image viewer, but many people still prefer the old Windows Photo Viewer. Check 'Always use this app' if you want to set Windows Photo Viewer as the default image application.

To use Windows Photo Viewer on Windows 10, enable it in the Windows Registry, then right-click an image file, click 'Open With,' and select 'Windows Photo Viewer' from the list.

Picasa photoviewer