If your secondary monitor is to the right of the primary monitor, and you play a game which changes the resolution of the primary monitor, the windows on the secondary monitor will be shifted to the edge of the monitor. This is an issue with DirectX. Workarounds:
* make the primary monitor the right-most monitor before playing the game
* change the display resolution manually before playing the game
Found this on the internet, pisses me off b/c I can play CoD4 at 1920x1200 only 1680*1050, but since the native rez of my 24" is 1920*1200 it shifts. Does not work to well in my situation b/c of my computer placement, but may help some.