A problem in Windows 8 is when you click on an image in Windows explorer it annoyingly loads it into the Win 8 photo viewer app.

To fix this:

go to Control Panel > Programs > Default Programs and select  Set your default programs.
Scroll down and click Windows Photo Viewer in the Programs list.
Then, click ‘Set this program as default’ if you’d like the Viewer to open all the file types it can handle, or select the ‘Choose default’ options if you prefer to specify which file types it should open. Finish by clicking OK.