Go to the interent explorer icon right click >properties>short cut>run: maximized
You can get the IE icon by typing Internet Explorer in search.
If the window still open half size, make it full size, by expanding the 1/2 size, by dragging the edges to the 4 corners of the screen. It should be acceptable at that point. When it opens in the future, it should open to that size. In addition to close a window do not use the red X, go to file and then exit.
I will not be 100%, for some, that solution has not been found.
You can also read this: http://www.eggheadcafe.com/software/...ndow-size.aspx