Computer Tricks to Save Power
Enable the "sleep mode" feature on your computer, allowing it to use less power during periods of inactivity. In Windows, the power management settings are found on your control panel. With a few simple steps, you can automaticly set your computer to go into sleep mode after a selected amount of time of inactivity. Remember, the computer is still using some electricity while in sleep mode. So if you aren’t going to be back for a while, you can go into hibernate mode or shutdown the computer.
On Windows XP:
1. Go to Control Panel
2. Go to Power Options
3. On the System Standby button, select the amount of time of computer inactivity before it will go into Standby Mode.
4. Click Apply/OK.
Configure your computer to "hibernate" automatically after 30 minutes or so of inactivity. The "hibernate mode" turns the computer off in a way that doesn't require you to reload everything when you switch it back on. Allowing your computer to hibernate saves energy and is more time-efficient than shutting down and restarting your computer from the beginning. Everything you left open will still be on your screen after turning on the computer from hibernate. Just remember to save your work

Hybrid Sleep (Vista Only)
This is the best of both worlds. Personally, this is the one I use. These feature sets your computer to Hibernate after a selected amount of time in Sleep Mode. Therefore your computer goes from Sleep to Hibernate mode.
More Instructions on how to Hibernate and Hybrid Sleep soon!