see video_window from the manual.
video_window(VECTOR* pos,VECTOR* size,var style,STRING* title)
pos vector containing the new x and y position in pixels, or NULL for no change
size vector containing the new x and y size in pixels, or NULL for no change
title new title of the window, or NULL for no change
style 0 for no change, or a combination of the following modes:
1 no border
2 thin border
4 thick border that allows resizing the window
16 title bar and border
48 title bar with close button
112 title bar with close and minimize buttons
256 hide the window