Put Your Computer to Sleep

Sleep is a feature in Windows Vista, supplanting the Standby feature of previous Windows OS versions. In the past, Standby didn’t always work well and computers were slow to come out of standby. In contrast, Sleep in Windows Vista is reliable, fast, and useful. In fact, in Windows Vista, Sleep should be considered the new default “Off” state. If you don’t already use the Sleep function in Windows Vista, you will find that you can start up a computer much faster by not shutting it down completely in the first place. Putting a computer to sleep is easy. You can choose Sleep from the Start menu press the power button on your computer (in Power Settings the power button must be configured to Sleep), press the Sleep button offered on many keyboards, or just close the cover of a laptop computer.

*** from: Overview Series: Windows Vista® Performance and Tuning
If you are an advanced user or just a geek, many tips can be learned from this file.