Résolution d'écran/dual screen Linux Kubuntu

Bonsoir,
J'ai trouvé des informations intéressantes pour modifier xorg.conf communiquées par -mamiemando- mais je n'arrive pas à solutionner mon problème de dual screen
Avec la configuration ci-dessous, j'obtiens un affichage sur les deux écrans mais c'est un bureau étendu.
Merci pour votre aide.

# xorg.conf (xorg X Window System server configuration file)
#
# This file was generated by dexconf, the Debian X Configuration tool, using
# values from the debconf database.
#
# Edit this file with caution, and see the xorg.conf manual page.
# (Type "man xorg.conf" at the shell prompt.)
#
# This file is automatically updated on xserver-xorg package upgrades *only*
# if it has not been modified since the last upgrade of the xserver-xorg
# package.
#
# If you have edited this file but would like it to be automatically updated
# again, run the following command:
# sudo dpkg-reconfigure -phigh xserver-xorg

Section "Files"
EndSection

Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "fr"
Option "XkbVariant" "oss"
Option "XkbOptions" "lv3:ralt_switch"
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"
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 "nVidia Corporation C51G [GeForce 6100]"
Boardname "nv"
Busid "PCI:0:5:0"
Driver "nv"
Screen 0
EndSection

Section "Monitor"
Identifier "Generic Monitor"
Modelname "Custom 1"
modeline "640x480@60" 25.2 640 656 752 800 480 490 492 525 -vsync -hsync
modeline "800x600@56" 36.0 800 824 896 1024 600 601 603 625 +hsync +vsync
modeline "800x600@60" 40.0 800 840 968 1056 600 601 605 628 +hsync +vsync
modeline "1024x768@60" 65.0 1024 1048 1184 1344 768 771 777 806 -vsync -hsync
modeline "1280x960@60" 102.1 1280 1360 1496 1712 960 961 964 994 -hsync +vsync
modeline "1280x1024@60" 108.0 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync
Gamma 1.0
EndSection

Section "Screen"
Identifier "Default Screen"
Device "nVidia Corporation C51G [GeForce 6100]"
Monitor "Generic Monitor"
Defaultdepth 24
SubSection "Display"
Depth 24
Modes "1280x1024@60" "1280x960@60" "1024x768@60" "800x600@60" "800x600@56" "640x480@60"
EndSubSection
EndSection

Section "ServerLayout"
Identifier "Default Layout"
screen 0 "Default Screen" 0 0
screen 1 "screen1" rightof "Default Screen"
Inputdevice "Generic Keyboard"
Inputdevice "Configured Mouse"

# Uncomment if you have a wacom tablet
# InputDevice "stylus" "SendCoreEvents"
# InputDevice "cursor" "SendCoreEvents"
# InputDevice "eraser" "SendCoreEvents"
EndSection
Section "Module"
Load "glx"
Load "GLcore"
Load "v4l"
EndSection
Section "device" #
Identifier "device1"
Boardname "NVIDIA GeForce 7 Series"
Busid "PCI:2:0:0"
Driver "nv"
Screen 0
Vendorname "NVIDIA"
EndSection
Section "screen" #
Identifier "screen1"
Device "device1"
Defaultdepth 24
Monitor "monitor1"
EndSection
Section "monitor" #
Identifier "monitor1"
Gamma 1.0
EndSection
Section "ServerFlags"
Option "Xinerama" "true"
EndSection