Due to the large amount of instructables I have seen here that detail ways to make batch file "Viruses", often times using the exact same code, I'm making this 'ible to show a comprehensive list of the ones that I know. Keep in mind, some of these can actually be dangerous if used, so be careful!
Some of these aren't exactly "pranks", and should only be looked at for educational purposes.
Disclaimer: I am not responsible if you wreck somebody's $2,000 water-cooled super awesome gaming computer, be it for a silly grudge, or accidental, using the code shown in this instructable.
Step 1: Making a Batch File
So, in order to input the code described later, you're going to actually need a place to put it. For Batch, you can use the command prompt by going to start>run>cmd.exe, or making a ".bat" file in notepad. Make sure to save it as all files and with a ".bat" extension.