I know it isn't April 1st, but office pranks are fun! Here are some pranks and links to more...

http://ask.metafilter.com/46747/Tell-me-a-...-computer-prank

http://en.wikipedia.org/wiki/Computer_prank

http://www.lifehacker.com/software/friday-...anks-261801.php

http://www.ex-parrot.com/~pete/upside-down-ternet.html

http://officepoltergeist.com/

http://www.jasonbartholme.com/2007/05/03/1...your-coworkers/

http://www.computerpranks.com/stories/

http://www.wired.com/print/culture/lifesty.../aprilfools0329

Install TightVNC, then hide the icon. It'll let you remotely connect to his computer and control the mouse and keyboard. Lots of fun can be had.

Sign in while he's working on a paper. Hit a random character every five or six words - just enough to make him question his keyboard and sanity. Do the same with the mouse. A quick flick every few minutes oughta drive him nuts.

screenshot someone's desktop and set that as their background, then turn off icons.

uses the system beep function to randomly chirp at the user. It should work on any windows machine, runs without a window, and plays through the system speaker so that it can't be muted (unless on a laptop). Open-source:

#include <stdlib.h>

int random(int min, int max)
{
    return (rand()%(max-min+1))+min;
}

int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    while(true)
    {
        Beep(random(100,3000), random(200,600));
        Sleep(random(1000,100000));
    }

    return 0;
}

go into Microsoft Word or the like and set the autocomplete setting so that it replaces words that they use all the time with "other things"

Remember, kids: Play Nice. People get angry sometimes:

If you were my roomie, and installed stuff on my box, or did anything at all to it, and then expected me to think it was funny, I'd beat you like a rented mule, until you got the message, even if it took weeks and all the hide on you.

on the subject of vnc i once installed it on a computer and they were playing unreal tournament so i would move the mouse occationally and shoot, they were convinced that it was the computers fault they kept shooting at walls and killing themselves

Cruel, cruel, cruel. But funny.

The wallpaper replacement one is good and simple. I can see that one being frustrating as heck. Just thought of this. If the taskbar is autohide, then make sure that it isn't up with the screenshot. Otherwise, they would see the second bar rise up.

DL

I did the wallpaper one, but slightly differently.

I added a folder called "Mom's porn" on my friend's desktop. Then I set that screenshot as the desktop, and removed the folder...

I used to work for an AntiVirus company in Aylesbury, England. As a result of somebody asking us to pick him up something 'non-fattening', we decided to buy him a block of lard - which then resulted in weeks of us trying to hide this block of lard in each other's work areas.

One day, this chap (who I shall call Richard, because that's his name) went out to lunch, presumably because he no longer trusted us to bring him food.

We powered down his PC, and connected his monitor to another PC, running exactly the same screen saver as his own. When he came back, he tried moving the mouse to get rid of the screensaver, he tried pressing CTRL+ALT+DEL. He unplugged the keyboard and put it back in again. He pulled the power out of the back of his PC, and put it back again. Still the screensaver didn't move.

Richard was a hardware engineer, so he set about taking the case off his PC, whereupon he found his hard disk had been placed with a 'lard disk'.