Maybe it's crazy, but open an IE window, maximize it and close it.... When you open it again, it should open maximized!!!
Edit: If you close it minimized, again you will have minimized windows opened...
Explanation: I remember when I had IE 6, that when I enlarged the window (without clicking on the button to maximize it), if I right clicked a link and say to open in a new window, it opened in a reduced size... So, maximizing it, all windows will open maximized...