This is the funniest one I've seen in a very long time.
I'm in IT, and our boss is notorious for not knowing how to get around on a PC. He's fine on a mainframe or Unix, but around Microsoft he's completely lost. He is one of those people whose desktop is almost completely filled with shortcuts. While he was out puffin' a smoke, one of my co-workers slipped into his office and:
1.) Took a snapshot of his desktop
2.) Put all of his shortcuts in the recycle bin
3.) Changed his desktop wallpaper to be the snapshot of the desktop
4.) Took the taskbar and drug it off the screen
The funniest part about the whole thing, though... he was too embarrased to call the help desk, so he called us in his office one at a time to see if we could figure out why the start bar and none of the shortcuts were working. One of my co-workers couldn't contain his laughter any longer and blew the bit, but we all had a tremendous laugh over it. Luckily, our boss has a sense of humor.