怎么接双显示器阿？

笔记本上装ubuntu，想再解个22寸的宽屏，但解上去之后两个屏幕都有显示，但分辨率都是1680＊1050的，怎么在两个屏幕上设置不同的的分辨率阿，显卡是G945的，我的xorg.cof文件如下:
Section "Files"
EndSection

Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "us"
EndSection

Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "ZAxisMapping" "4 5"
Option "Emulate3Buttons" "true"
EndSection

Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "HorizEdgeScroll" "0"
EndSection

Section "InputDevice"
Driver "wacom"
Identifier "stylus"
Option "Device" "/dev/input/wacom"
Option "Type" "stylus"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "InputDevice"
Driver "wacom"
Identifier "eraser"
Option "Device" "/dev/input/wacom"
Option "Type" "eraser"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "InputDevice"
Driver "wacom"
Identifier "cursor"
Option "Device" "/dev/input/wacom"
Option "Type" "cursor"
Option "ForceDevice" "ISDV4" # Tablet PC ONLY
EndSection

Section "Device"
Identifier "Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller"
Driver "intel"
BusID "PCI:0:2:0"
Option "MonitorLayout" "LCD, CRT"
Option "CRT2Position" "RightOf"
Option "MetaModes" "1280x800-1680x1050"
Option "MergedXinerama" "on"
Option "MergedNonRectangular" "true"
Option "MergedFB" "true"

EndSection

Section "Monitor"
Identifier "通用显示器"
Option "DPMS"
EndSection

Section "Screen"
Identifier "Default Screen"
Device "Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller"
Monitor "通用显示器"
DefaultDepth 24
SubSection "Display"
Modes "1280x800"
EndSubSection
EndSection

Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"

# Uncomment if you have a wacom tablet
# InputDevice "stylus" "SendCoreEvents"
# InputDevice "cursor" "SendCoreEvents"
# InputDevice "eraser" "SendCoreEvents"
InputDevice "Synaptics Touchpad"
EndSection

谢谢大家拉