Click on Start, then on the right hand side of the menu select ‘Control Panel’. Control Panel has two views. If you are in Themed View double click on ‘Hardware and Sound’ and…
…And then select ‘Power Options‘.
If using a standard view, select ‘Power Options‘.
Once you are in Power Options you can customize one of the pre-configured plans by selecting the ‘change plan settings‘ options…
…and setting the amount of time before ‘turn off display‘ and ‘put the computer to sleep‘ actions are initiated. These can be set for when the computer is plugged in and when it is on battery (if you have a laptop).
To change more settings click on “Change advanced power settings”. Here you will be able to enable or set values for a variety of Power Management options.
EPA recommends setting computers to enter sleep after 15 to 60 minutes of inactivity. To save even more, set monitors to enter sleep mode after 5 to 20 minutes of inactivity. The lower the setting, the more energy you save.
Situations that may cause Windows 7 to not sleep
PCs may not enter sleep mode when they have a file open over the network. Graphics-intensive screen savers can prevent PCs from entering sleep mode as well, and should be disabled.
Otherwise Vista should not allow software applications to stop it from going to sleep. However, it is possible for a network administrator to change this default, allowing applications to “veto” sleep when they are busy. The default can be changed using Group Policy, but cannot be set through the Power Options applet in the Control Panel.