shutdown system after 1 hour
1) Open the Run window (Windows Key+R) or (Start / All Programs / Accessories / Run).
2) type
shutdown -s -t 1800
[1800(can be changed) is the number of seconds after which the computer will turn off.]
Click on OK and your computer will turn off after the specified time (here 30 minutes).
You can change -s for alternatives as below:
options effect
-l to log off
-r to reboot