The PowerPoint backgrounds provided here are .jpg images. To download, click on an image for a larger version. Then right-click on the larger version and left-click “Save image as…” in the menu that appears. Pick a good location to save it on your computer.
To use the background in PowerPoint:
For older versions (2003 or ealier), right-click on the slide that needs the background. Then left-click on “Background…” in the menu that appears. Click the drop-down arrow next to the rectangle that displays the color of the background (it will be white if it is a new slide). Choose “Fill effects…” from this menu. In the next frame, click on the “Picture” tab, then click the “Select Picture…” button. Find the background that you just downloaded and saved and double click it. Then click “OK.” Then click “Apply.” You may also choose to “Apply to All” if you want this background as your default for all slides in the presentation.
For newer versions (2007…I don’t know about 2010 yet), right-click on the slide that needs a background. In the menu that appears, left-click “Format background…” In the next frame click the little circle next to “Picture or texture fill.” Then, a little further down, click the button that says “File…” Find the background you just downloaded and saved and double click it. You will see the background apply, and then you can click the “Close” button. Or you can click the “Apply to all” button to make the background the default for all of your slides in the presentation.