Display shifts

Has anyone run across this?..A customer has a Windows XP computer..Nvidia video card with the latest drivers.Since installing a program called GhostWriter (open source pdf writer) Internet Explorer opens 1.5 times as big as his screen..everything else is normal..screen definition doesn't seem to change..I am assuming it must be a registry change but can't find the key for it anywhere..any ideas would be great

Try opening IE, resizing the window to just under screen size, then closing it. It may also help to check the shortcut that's opening the program to see if the "Run:" field is set to "Normal Window". If it is, try setting it to "Maximized", instead.