что конкретно в нем менять?

Section "ServerFlags"
    #DontZap # disable <Ctrl><Alt><BS> (server abort)
    AllowMouseOpenFail # allows the server to start up even if the mouse does not work
    #DontZoom # disable <Ctrl><Alt><KP_+>/<KP_-> (resolution switching)
EndSection

Section "Module"
    Load "dbe" # Double-Buffering Extension
    Load "v4l" # Video for Linux
    Load "extmod"
    Load "type1"
    Load "freetype"
    Load "glx" # 3D layer
EndSection

Section "InputDevice"
    Identifier "Keyboard1"
    Driver "kbd"
    Option "XkbModel" "pc105"
    Option "XkbLayout" "us,ru(winkeys)"
    Option "XkbOptions" "grp:ctrl_shift_toggle,grp_led:scroll,compose:rwin"
EndSection

Section "InputDevice"
    Identifier "Mouse1"
    Driver "mouse"
    Option "Protocol" "ExplorerPS/2"
    Option "Device" "/dev/mouse"
EndSection

Section "Monitor"
    Identifier "monitor1"
    VendorName "ViewSonic"
    ModelName "ViewSonic E655-2"
    HorizSync 30-70
    VertRefresh 50-100
   
    # TV fullscreen mode or DVD fullscreen output.
    # 768x576 @ 79 Hz, 50 kHz hsync
    ModeLine "768x576"     50.00  768  832  846 1000   576  590  595  630
   
    # 768x576 @ 100 Hz, 61.6 kHz hsync
    ModeLine "768x576"     63.07  768  800  960 1024   576  578  590  616
EndSection

Section "Device"
    Identifier "device1"
    Driver "ati"
    Option "DPMS"
    Option "XaaNoOffscreenPixmaps" "1"
EndSection

Section "Screen"
    Identifier "screen1"
    Device "device1"
    Monitor "monitor1"
    DefaultColorDepth 24
   
    Subsection "Display"
        Depth 8
        Modes "1024x768" "800x600"
    EndSubsection
   
    Subsection "Display"
        Depth 15
        Modes "1024x768" "800x600"
    EndSubsection
   
    Subsection "Display"
        Depth 16
        Modes "1024x768" "800x600"
    EndSubsection
   
    Subsection "Display"
        Depth 24
        Modes "1024x768" "800x600"
    EndSubsection
EndSection

Section "ServerLayout"
    Identifier "layout1"
    InputDevice "Keyboard1" "CoreKeyboard"
    InputDevice "Mouse1" "CorePointer"
    Screen "screen1"
EndSection

не помогло

что за видюха, какие стоят дрова

Он же конфиг выложил:
Driver "ati"

Ну умелец тот еще)
Radeon 9600XT

А ты после того как в xorg.conf поменял сохранил? О_О