TO CHANGE THE BACKGROUND PICTURE ON THE SCREEN (WINDOWS VISTA):
1) Right-click on the desktop anywhere (except on an icon or button).
2) Click on Personalize.
3) Click on Desktop Background.
4) Scroll down and click on the picture you want, or click on the Down Arrow next to whatever is in the Picture Location box, then click on Pictures if you want to select one of your own photos. (Your pictures will normally automatically be downloaded into the Pictures folder.)
5) Be sure that the far left choice is selected under “How should this picture be positioned?” if you want the picture to completely fill the screen.
6) Click on OK.
7) Click on the X button to close the Personalization window.