With all the possible combinations of Power Management settings, both in BIOS and in Windows, and the well-known inability of Windows to deal well with standby/shutdown/restart conditions, you may be better off just forgetting it. My recommendation -- Turn off or disable all PM settings, set everything to "Always On", and turn off the monitor by its own switch if you're away for more than 20 minutes. It's the biggest power consumer and heat generator in your system. Most of the power saving features evolved for extending battery life in portables. There is an excellent discussion of this topic in the PC Guide here
"I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question."
-- Charles Babbage, mathematician, computer pioneer, analytical engine designer (1791-1871)
-- (Question: 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?')
"Just because I don't care, doesn't mean I don't understand."
-- Homer Simpson