After that, it reappears in Windows 7.
Now follow the instructions below to bring it back.
Step 1: Press theWinkey andIkey at the same time to openSettings.

Step 2: ClickSystemand then clickDefault apps.
Then click it to see a list of options for a new default photo viewer.
Step 4: ChooseWindows Photo Viewerand then exit theSettings.

But luckily, Windows Photo Viewer is still on your system.
It is just hidden and you better make some changes to Registry to have it show up.
Therefore, I highly recommend you toback up important filesand registry in advance.
Step 2: Double-click theREGfile to merge it with your Windows Registry.
Click through theUser Account Controland a few other windows to allow the file to make changes to the Registry.
Navigate toControl Panel> setView by: Small icons>Default Programs>Set your default programs.
After finishing these steps, you could bring Windows Photo Viewer back in Windows 10.
In addition, you might know how to bring Windows Photo Viewer back in Windows 10.