Sleep mode, once known as Stand By or Suspend mode, saves energy but doesn’t quite turn the PC off. In Sleep mode, Windows saves what you're doing and then puts the computer to sleep — meaning into a special low-power mode. The computer isn't exactly off, and it restores itself quickly, which makes Sleep mode more effective as a way to shut down the computer. So, put your PC to sleep:
Click the Start menu button.
The Start menu opens.
Click the triangle icon in the lower right of the Start menu.
The Shutdown menu appears to the right of that icon.
Choose the Sleep command from the Shutdown menu.
Windows tells your PC to take a nap; it shuts off the lights and the screen goes blank.