How do you lock one monitor's resoution?

I'm running 2 23" IPS monitors, and of course, natively running at 1920x1080 each...

I just reinstalled Baldur's Gate I and II (my all time faves!!) and I am using a widescreen mod. And in doing so, forces my primary monitor to run at 1280 x 720 in game and thus mess up the the resolution of the secondary monitor... So is there a way to lock the secondary monitor's resolution even if the primary monitor's resolution is forcibly changed?