Go to someones computer running XP. close all programs till you can just see the desktop. Hit Print Screen. Open Paint paste the saved desktop image. Set the saved image as the Wallpaper. Re-open the programs they had running when you started then hit ctrl-alt-delete, click Processes, highlight Explorer and click end process. When they return to their desk they'll be able to work on those things, but not be able to click on any icons on the desktop or open the start panel.