s how to do... Open the System Preferences, click on Screen Effects and select your favorite screen saver. Now, open the terminal and paste the following line: nice +20 /System/Library/Frameworks/ScreenSaver.framework/Resources/ScreenSaverEngine.app/Contents/MacOS/ScreenSaverEngine -background & than hit return to make the active screen saver your desktop. When you hit return, a number will appear in the Terminal window - it follows a number. To turn off this effect, type kill and the number. Be warned, using the screen saver as a desktop background will even effect the performance of the fastest Macs. For better performance from the effect, don't include "nice +20" in the command.