Your monitor and your video resolution
Sometimes the screen resolution is not appropriate, or perhaps you made a mistake during installation, you can use this icon to set the proper resolution if the current one is not correct.
In case you need to reconfigure the video adapter you can do it by running the following command under text mode.
To run the Configuration under text mode login as root and execute XFdrake this will allow you to configure your hardware; this is same as in mcc.
XFdrake is an advanced tool and most likely will probe your hardware. If you are not getting anywhere with this utility, find out about your hardware – is it supported by Linux? What possibilities do you have to change your video adapter?
If you are going to change the video card, try NVIDIA. It works well and most likely will be supported. Whenever you make changes test your configuration before accepting the settings.
The graphical server configuration
In most cases you don't need to make changes here, it is automatically configured during installation. The server is what controls your interface. If the server is not running you simply don't have graphics.
Any time you configure a display adapter or monitor, you are only modifying your client settings, which must report the appropriate refresh rate and resolution for the server to send the correct display.
If you accept the changes the server updates its database, and there after keeps the information after reboot. So every time you start your Xwindow the server is contacted and the information is verified in order to display the correct resolution.
Note: If the server holds the incorrect settings and you start the graphical interface, you have the chances of ruining your video adapter or monitor. Be careful, read about your hardware specs when you are configuring manually.