just sitting here reading my own work.
you can try the following as well.
i had to reinstall my windows 7 64bit as it crashed

had to be in windows 7 to make sure i give you the correct steps as windows xp works in a different way.
when your on the desktop right click the mouse then click screen resolution
that will bring up windows 7 display,
click the blue text advanced settings
click the monitor tab
when that is open take the tick out the box hide modes this monitor can not display
click apply then close all the windows and restart the laptop
then see if you can change to the res that you want
this does not work on some laptops as windows does its best to read the max res from the screen hardware and GFX information but its worth a shot.