To change the background on your desktop in Windows 7, click Start, go to Control Panel, type “desktop background” into the search tool at the top-right corner of the window and then click on Change Desktop Background. Choose a picture from the provided list and then click Save Changes.
If your preferred picture does not appear in the provided list, click Picture Location to open other categories, or click Browse to locate the picture on your computer.
If you are using Windows XP, go to the Control Panel, click Display and then click the Desktop tab. Select a picture from the Background list and then click Position to change its position. Under Color, select a color to fill the spaces not covered by the picture. Alternatively, right-click anywhere on your desktop and then click Properties to open the Display Properties window.
In Windows 8, right-click anywhere on your desktop and then select Personalize. On the bottom-left section of the window, select Desktop Background. Select the new picture from the drop-down list or click the Browse button to locate a specific photo on your computer. Customize the photo to suit your preferences and then click Save Changes to save the selected picture as your new desktop background.