Best free screensaver
Monitors running screensavers consume the same amount of power as when running normally. Additionally, using a screensaver with a flat panel or LCD screen instead of powering down the screen can actually reduce the lifetime of the display.
Thus the term "screen saver" is somewhat a misnomer—the best way to save the screen (and also save electricity and preserver our environment) would simply be to have the computer turn off the monitor.
Note: if anyway you want to see a funny picture as a screensaver, visit the free screensavers download section.
How to start using the best screensaver (for Windows XP and Vista)
Make right mouse click on the desktop and then select Properties to open the Display Properties window and go to the Screen Saver tab.
Now select Blank from the list of the available screensavers. I recommend to set 5 minute idle time before the selected screen saver is displayed.
Click the Power... button to set the monitor turn off interval and save your screen, energy and our planet Earth. I believe :-)
In the Power Option Properties window specify the period of inactivity that you want to elapse before your monitor turns off when it is running on AC power. I recommend 10 minutes.
Click Apply and then OK to close this window, repeat this action in the Display Propertis window.
Note: it is very important to turn off the monitor when you are not using it, because screensavers are not to be confused with power management features, which place the computer in a low power state after it has been idle for a specified amount of time. In fact, screensavers can actually waste power, because they can prevent the computer from entering the lower power (or sleep) state, and they often cause the CPU and GPU to perform more calculations, and keep the hard disk running for longer than if the computer were idle.