That usually boils down to your graphics card setting (in fact, it most likely does). It depends on your graphics card as to how you access the calibration for it. For an Nvidia card you'd left-click on the desktop (on a Windows system anyway) and you should get a control panel all of it's own being an option to click on - which would then lead you to a calibration settings option for it. Not sure about other manufacturer's cards though! You might want to check what card you have, and see if there's any documentation on how to get to it. It's also possible that if you're using a desktop PC, that you might use an external monitor as opposed to an in-built display (like on a laptop), and it might be you'd need to mess about with the settings on that too. Hard to say without knowing what system you're using though.