New Problems with Resolution..

My monitor's native resolution is 1440x900, so that's what i use on crossfire. However, when i scope in with any gun in the game, my screen somehow magnifies, changing the resolution to a number that crossfire does not provide. As a result, my Field of view looks as if it was scoped in without the extra red dot or black circle or black surroundings while scoped in. Why is it bad to have everything big? I lagg a lot more, and my cursor is moving as though it was scoped in, which is an awkward feeling if you're spraying.
Help me solve this problem =]? Ty