however it might be that it is missing in your registry? Download this file and install it, it is very handy. (found by SkyHi)
if the standby from it does not work, scan for viruses! if it does then it is most likely not in your registry, which you should find out why. http://www.xtort.net/xtort/xpsyspad.php
What does it have in place of Standby? Hibernate? If so, push shift while in the "Turn Off Computer," and don't listen to talldude b/c he only is trying to get posts.