[CentOS] /etc/X11/xorg.conf question

If I use "system-config-display" or "system-config-display --reconfig"
although I get a message that I need to log out of GNOME, to have the
new file written, for new Display Resolution, logging out or
restarting the box does not result in the new settings for the Display
taking hold. Sometimes, the number of colors is updated, but *never*
the Resolution. Below is my xorg.conf file.  What do I need to include
in xorg.conf for the resolution to be 1280 x 1024 instead of the
current 1600 x 1200? Display is a Dell M991 and the Video Card is
shown as Nvidia NV11 (GeForce2 MX/MX400).  CentOS 5.2 (32 bit) fully
updated.   TIA!

# Xorg configuration created by system-config-display

Section "ServerLayout"
	Identifier     "single head configuration"
	Screen      0  "Screen0" 0 0
	InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "InputDevice"
	Identifier  "Keyboard0"
	Driver      "kbd"
	Option	    "XkbModel" "pc105"
	Option	    "XkbLayout" "us"
EndSection

Section "Device"
	Identifier  "Videocard0"
	Driver      "nv"
EndSection

Section "Screen"
	Identifier "Screen0"
	Device     "Videocard0"
	DefaultDepth     16
	SubSection "Display"
		Viewport   0 0
		Depth     24
	EndSubSection
	SubSection "Display"
		Viewport   0 0
		Depth     16
		Modes    "1600x1200" "1600x1024" "1440x900" "1400x1050" "1280x1024"
"1280x1024" "1280x960" "1280x960" "1280x800" "1280x800" "1152x864"
"1152x864" "1152x768" "1152x768" "1024x768" "1024x768" "800x600"
"800x600" "640x480" "640x480"
	EndSubSection
EndSection