PC's and laptops consume a whole lot of electricity every time you use them which can range from 150-800 watts when in use to 50-400 watts when in sleep mode or hibernation. That's a huge amount of power and an even bigger chance to cut down that number. Cutting down your power cost on just your computer can save you around $100 a year which means more upgrades for your best friend.
The average computer runs at 250 watts in sleep and 400 when running and by making a few simple changes you can chop that number in half. The biggest feature most people neglect on desktops is the standby/sleep mode. When you use this it cuts down the power to virtually nil (10 watts) and suspends and resumes action almost instantly compared to hibernate which uses a little less power but takes over twice as long to suspend and resume depending on the RAM size. A huge energy saver is going with a simple screensaver instead of a 3D one. The biggest energy saver is not leaving your computer in idle if you aren't there. Take the extra 5s and go to the Start Menu and hit sleep/standby. You can save over 100 watts easily by doing that.
There are also many settings in Vista and XP that allow you to change different power options like screen brightness. Just go to the Control Panel and hit Power Options. Something people may not know is that if you have an electrical device completely off, but still plugged in, the device still sucks up energy. It's mind boggling how much energy you can save by unplugging phones, TV's, printers, computers, and many more if you're not using it. So next time you leave an electrical device, think twice.