I remember for my P-book to get to the correct screen dimensions I had to go control panel>display>settings>advanced>monitor
and uncheck "hide modes that this monitor cannot display", then go back to display>settings to find the right dimensions.
Maybe you have a suitable display mode hidden in there somewhere that will appear once you uncheck that box.
If not maybe you need to search for a newer display driver for your computer, then try repeating the above.
good luck,
Ben
Will probably be at Santana this sat, maybe see you there?