to REALLY freak them out, do the following: when they leave their computer, before it flips to the screensaver, hit the 'print screen' feature on their keyboard, and paste it to the MSpaint at a resolution of the size of their screen (ie 800x600 or 1024x768, et al) , save it, then set it as their wallpaper. hide their icons in the trashbin temporarily (this is not permanant until you actually delete the files, so be careful on what you do!) then apply the 'hide taskbar' feature on their system through taskbar properties. this will send them into a reboot and virus scan fit. i did this to a co-worker who is very computer illiterate, and he freaks out at every little thing that goes wrong on his computer. it was a riot.