Whenever i open a game, part of the 1st moniter goes onto the 2nd moniter. So i cant watch movies, look at things, read things etc on the 2nd moniter when im playing on the first moniter. I think this is because the resolutions of the games dont have my native resolutions but i dont know how to fix this.
As you have said, this is because the game isn't using the same resolution on that screen as it is when on the desktop. The only way to keep the screen from migrating over to your other one while in game is to set the game resolution to 1680x1050. You may have to do a little tinkering in the .cfg files if you can't do it via the options menu.
This used to aggravate me to no end when I had my brief stint with KOTOR; especially during the cinematics because they would change the screens resolution to match the cinematic.