I think that Internet Explorer remembers the window sizing from the _last_
open IE window that gets closed. However, you can right-click on the IE
shortcut icon you use, then select Properties, next to 'Run:' select
Maximized. this will force IE to start Maximized all the time. You might
need to do the same to any other IE shortcut icons you have if you want them
all to respond the same.
hth,
~Lars