How to set arbitrary window size when not in fullscreen?

Is it possible to make the player window any size? It seems silly that window sizes would be restricted to resolutions suported by the monitor. More so since it is possible to resize the window by dragging its corner with the mouse. I'd like to be able to do something like:

Screen.SetResolution(1280, 480, false);

regardless of what my monitor supports. Again, i'm not running the player in fullscreen mode, but windowed, so it should be possible, right?