United States Theme Pack is a free Windows 7 theme pack. It works with Windows 7 Home Premium, Professional, Enterprise and Ultimate. It contains six pictures that can be used as desktop backgrounds, and a sound scheme named Afternoon, with guitar sounds that will be used by your system to notify you of certain events, such as Windows startup, USB connection, etc.
When you double-click on the downloaded .themepack file, your computer will open the Control Panel, the Personalize window, and will accept the new theme as the one that you will be using from that moment on, with all the images selected, the new sound pack selected and the images changing every thirty minutes. You can, of course, change each of the settings. Those related to the images that you will use as backgrounds can be changed by clicking on the Desktop Backgrounds link, where you will be able to choose the images to show, the position they will take, the time that they will remain selected, and if you want to shuffle them.