Glad to see other people are attempting to do something, it doesn't all mean having to eat recycled poo roll, I'm at 0.3 so far ... pants I know.
A modern computer configured to support 'power saving' mode left switched on will use far less electricity than the same equivalent computer powered off and powered back on again. It's on 'spinning-up' the disk and 'firing-up guns' in a CRT screen (different in an LCD screen I admit) - that eats the most power.
Windows will always attempt to run 'in memory' and not 'page to disk' - whenever possible unless your resources dictate otherwise. At night when your asleep and you leave the app running it will no doubt utilise so little resource, (assuming you have enough Volatile RAM) - that your Hard Disk will 'spin down'. With the monitor in 'power saving' mode due to no screen updates it will use less than having to power the machine up the following day, not to mention the amount of time it takes to boot the O/S.
[Edited on 25-5-2006 by desmobob]