When you replace the wallpaper in the Win7 system, there is a small probability that an error "cannot be set as wallpaper, and an internal error has occurred". The following small series for you to introduce a specific solution.
1. First double-click the desktop "Computer" icon, click "Organize"-"folder and search Options" in the interface.
2. Then switch the View tab in the window, remove the "Hide protected operating system files" check box in the Advanced Settings section, and then select "Show hidden files, folders, and drives" and click "OK".
3. Then open C:users your username by default is administratorappdataroamingmicrosoftwindowsthemes this directory, will be inside the file all deleted (Don't worry you can back up first).
4. Users not found? The folder is called users in the explorer and is displayed as users in the Address bar.
5. Delete the right key on the desktop to choose "Personalized", in the inside casually replace a theme, then you can replace the wallpaper.