Background Image - registry

To change the Background Image in windows 2000/Me/XP open the registry and Navigate to [HKEY_CURRENT_USER SoftwareMicrosoft\Windows CurrentVersionPolicies\System] and create a string value named Wallpaper and set it to the location of the image you want as the background. Next create another new string value called WallpaperStyle and set it to either 0, 1 or 2.
0 - Centered (Default)
1 - Tiled
2 - Stretched
Now exit the registry, and restart your computer for the change to take effect.