Long time since I used XP but ...
Open an IE window to the smaller size
Drag the corners of the window until it completely fills the screen. Do not use the maximize button to enlarge the window
Hold down the Ctrl key, and while holding it down use the mouse to click File and then Exit on the toolbar. DO NOT use the "X" in the upper right corner to close the window
IE should now open in a full window
If not repeat the above but this time us the Shift key instead of the Ctrl key