Step 1.

Determine your screen resolution:

1. Click on the START button within Windows.

2. Go to Settings, then Control Panel.

3. Click on the Display icon

4. Click the settings tab.

5. Write down your desktop area setting
   (800 by 600, 1024 by 768).  

Step 2.

1. Select the screen size that matches the resolution setting you wrote down in Step 1.

2. Wait for the image to download.

3. Place your mouse pointer over the image, click the right mouse button and scroll down to "set as wallpaper." or "set as background"

4. Have fun!