To save energy, enable your computer to automatically turn off its monitor or hard disk after a certain period of time of idleness (E.g. you left for work and you forgot to shutdown your PC). Here is a list of steps that will teach you how to set-up sleeping times for your desktop/ laptop.
1. Right click on your desktop.
2. Choose properties.
3. Click on the Screen Saver tab.
4. Click on the power button.
5. At the Settings for Home/ Office Desk power scheme field set, set the turn-off times for your monitor and hard disks by choosing from the drop down menus.
6. You may also set the length of time before system stand by or hibernate activates.