Bare windows includes anti virus, daemon tools, and and all the driver suites...
Otherwise you are cheating... Nobody runs a computer with no driver suites... heck even My bare minimum is was less then the average user has (Who is has about 20 icons in his system tray).
I shouldn't have to turn off my anti virus program and printer driver to have enough ram to run a game.
IF you want the smallest boot ram usage then give me some time with vlite / nlite and I will make a stipped down copy of windows where NOTHING works but takes only 200mb of ram... thats a pointless exercise though. A functionaly system has all the drivers installed, all the default stuff, probably aero, and usually an anti virus suite.