Escape -> Settings -> Video settings
Change the resolution (width and height) to the size you want your window to be, then uncheck the Fullscreen box.
Select "Apply now" and you should get a windowed AC.
quick edit: If you want to get your mouse out of AC quickly, you might want to bind a key to /togglegrap.
Change the resolution (width and height) to the size you want your window to be, then uncheck the Fullscreen box.
Select "Apply now" and you should get a windowed AC.
quick edit: If you want to get your mouse out of AC quickly, you might want to bind a key to /togglegrap.