I have two computers, side by side. The right side is a Dell, the left side we built. Both have XP Pro. I would prefer to put them to sleep at night, seems to take FOREVER to start up in the morning (well, the one we made takes forever. The Dell starts up VERY quickly).
Both keyboards have a 'sleep' button. The one on the left will sleep. BUT, sometime the next day I will HAVE to reboot or it won't go to sleep that night. It will only go to sleep once, then if I try it again the next night without rebooting, it will say something like "Preparing to stand by" on a blue windows screen, but it NEVER does stand by / sleep. The one on the right will sleep but to bring it out of sleep I have to hit the power button. The other one, when it works, just move the mouse to bring it out.