Well, with modern display-drivers and screens, it seems the entire display is inhibited when in standby/off, and Windows shakes/resizes all it's visible windows to the last, or the primary, awake monitor it still sees. And also resets the other virtual screens to something like 640x480 pixels.
I see this behavior on my dual-DP setup, where I leave the (work) computer running overnight, but turn off the screens to preserve some power. Any window I leave open is moved and resized to the left-upper 640x480 of my primary monitor
My current solution is to close all (well, almost all) applications, auto-saving their last window-positions and sizes, and re-opening them the next morning. Exceptions here are Outlook, that I minimize to the tray by default, and other trayed apps like SSC, that aren't affected, unless I forget to minimize them.
Haven't found a solution, other than to minimize all windows to the system-tray, to avoid this behavior. But, I haven't yet done a thorough search for this either