Pb résolution ecran ss Ubuntu

Bonjour,

J'ai un problème non résolu, j'espère trouver auprès de vous u_ne réponse qui va fonctionner...
J'ai un écran 17' 1024x768 mais ma résolution sur mon bureau est de 800x600!

Dans les préférence d'affichage d'écran je suis par défault en Custom1 800x600, quand je veut changer et mettre Monitor 1024x768 résolution 1024x768 6OHz, pas moyen d'effectuer de test, je ferme j'y retourne, ca ma remit en valeur de défalut!!!

et dans système>préférence>résolution d'écran je n'ai le choix qu'entre 800x600 et 640x480...

Donc 3jour que je m'énerve a trouver une solution pour mattre la bonne résolution!!!

Voici mon fichier xorg.config:

# 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"
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 "S3 Inc. 86c325 [ViRGE]"
Driver "s3virge"
BusID "PCI:0:7:0"
EndSection

Section "Monitor"
Identifier "Écran générique"
Option "DPMS"
HorizSync 30-70
VertRefresh 50-160
EndSection

Section "Screen"
Identifier "Default Screen"
Device "S3 Inc. 86c325 [ViRGE]"
Monitor "Écran générique"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1024x768" "800x600" "800x600" "640x480"
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"
EndSection

Merci beaucou de m'aider!!!