Windows Photo Viewer should open 1 window for previewing multiple images. If it opens multiple instances when previewing images, see this fix.

If you receive message Windows Photo Viewer can't display this picture because there might not be enough memory available on your computer, see this fix.

Windows 10 comes with Microsoft Photos app and Windows Photo Viewer has been retired, but you can restore it by tweaking your Registry.

The default windows photo viewer and Pictureflect photo viewer allow me to scroll through photos on the NAS with some PCs, but not others.