It should be a setting in your video card’s drivers. Right click on the desktop and then click on either “Properties” or a video “Control Panel” (such as NVIDIA) that may be present. Then change the settings there. You’re looking for extended desktop modes or monitor modes. If Clone Mode is an option, it will mirror the same image on both monitors which is one way of doing it, but defeats the purpose of two monitors. Span will stretch it across both which is what you have now. There may be other modes available depending on who made the card and driver. There should be a setting for setting which monitor is considered primary. Set it to your left monitor.
However, because of the way games work with DirectX, this will still be a less than ideal setup. When the game runs, it will set the display of the primary monitor to its native resolution which will cause a resolution shift in your right (secondary) monitor. Icons and applications will often shift off the screen. This means that basically, the second monitor isn’t very useful when playing a game that takes control of the desktop resolution. A workaround to this is to set the resolution of the primary monitor to the games resolution before playing so that there is no shift, or just deal with it as the resolution will return to normal once the game has been minimized (ALT+ESC) or ended.
Some times, the only way to do this is to turn off the secondary monitor before you start the game. It really depends on the card and your driver.
