At home I have a desktop PC with Windows Vista. One of the many cool features of Vista is the Sleep mode. In Vista it's called Sleep, but it's actually a hybrid Sleep and it works different compared to the Standby or Hibernate functions of previous Windows versions.
Vista sleep explained
In previous Windows versions, Standby meant that Windows turns off the CPU and keeps power to the RAM. Waking up from standby was very fast. Hibernate instead also turns off the CPU, but saves the RAM to the hard disk. The RAM doesn't have to keep power. In that way, you save more energy.
The Vista Sleep function is like I said a hybrid. When Vista enters Sleep, it writes the RAM to the hard disk, but it also remains power on the RAM. If you wake up your PC it will turn on very fast because everything is in RAM. Except when you had a power interruption (like empty battery), in that case the system wakes up slower because the RAM is restored from disk. You can read more about this on the Vista Team Blog.
When Vista won't enter Sleep Mode
In the beginning, my PC entered the Sleep Mode without any problem. I was also able to wake it up via Wake On Lan. But since a couple of days, it simply doesn't want to sleep. It looks like it's turning off, but after 10 seconds everything is back on.
This is caused by the Power Options of your machine. If your preferred plan is set to 'High performance', Vista doesn't want to go to Sleep anymore. To fix it, set it to 'Balanced'.
- Open the Control Panel;
- Click the category Hardware and Sound;
- In the Power Options category, click Change power-saving settings
- Click the Balanced preferred plan
- Close the window
Hope this helps,