On my desktop with Windows 7 Professional x64, I have a folder of images that I use for my theme. Under Personalization (right click on desktop -> Personalize) it is the only theme under 'My Themes'. Repeatedly, I have noticed the background has stopped rotating and is stuck on one image. When I go to Personalization, I notice a new theme has been created called 'Unsaved Theme' with one image from my folder and is the current theme.
To fix this, I set the theme back to my folder and delete the single image theme. How can I prevent this from reoccurring as it has happened multiple times?