I think that this is some kind of oversimplification of what actually happened. AFAIK there is not even an operation like "put window into notification area" a

I think that this is some kind of oversimplification of what actually happened. AFAIK there is not even an operation like "put window into notification area" as part of WinAPI as the icons are mostly orthogonal to windows (and are not even intended to represent "more-minimized" windows). The icon has to reference some window, but only because it generates window messages that have to be consumed somewhere. Fun fact: at least on 2k and XP, when the window goes away, the icon stays visible unless it is explicitly deleted by user code and is removed only when some message would be sent to now non-existent window (ie. when users mouses over the icon).