Place your mouse in any blank spot on your desktop and Right-Click.  In the pop-up window select "Properties"  Along the top you will see tabs, left-click on "Settings"  It will show you the present settings.  Place your mouse to the left of the current setting and it should move to a higher setting continue this until you get the setting you want.  If is doesn't change you will have to install a different video card that supports a higher resolution.  Hope this helps
                 Bruce
                
 June 2008