automatic shutdown the system in time for xp/vista/windows7 in run command

step 1: Go to start menu and click run.
step 2: Type the following

shutdown -s -t 60 -c "guna now system shutdown".

-s ->shutdown
-t->time in seconds
-c-> this is message command then type message in whithin double quoates
step 3: Then Enter or Ok.

Thank u