> both the Apple bar and the MS bar do the same thing, offer a target in accordance to Fitts' Law.
Not until Windows 2000. Prior to that, the Start button had a single "dead" pixel along the left and bottom sides of it in which clicking didn't open the Start menu. Microsoft design: it looks right, but it just doesn't quite work right.
http://blogs.msdn.com/b/jensenh/archive/2006/08/22/711808.as...
While the layout of the menu itself changed some over the years, the base location in the bottom left has remained the same.
Even with Windows 8 you could get to the startscreen(?) by flicking the mouse to the bottom left corner. That would case a square to come into view holding a preview of said screen.