I have failed to configure two monitors under Linux with a two outputs nVidia GeForce GTS 240 on a Dell Studio XPS 8100

Hi,

I don't manage to have the second output of my graphic card nVidia GeForce GTS 240 work on my Dell Studio XPS 8100.
I checked that my second monitor, cable and adaptor all work right by testing them on the first video card output.

I followed some Linux tutorials to configure X11 for two monitors setup on one video cards with two outputs and tryed two methods :
  1) with TwinView
  2) with xinerama
In both cases, the monitor is like receiving no signal.

If someone has managed it, please post here how you did it.

Here are my xorg.conf files in both cases :

1) with TwinView

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
EndSection

Section "Files"
EndSection

Section "Module"
   Load  "record"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    Option     "TwinView"
    Option     "MetaModes"  "1280x1024,1280x1024; 1280x1024; 1024x768,1024x768; 1024x768; 800x600,800x600; 800x600"
    Option     "TwinViewOrientation"      "RightOf"
    Option     "SecondMonitorHorizSync"   "28.0 - 33.0"
    Option     "SecondMonitorVertRefresh" "43.0 - 72.0"    
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

2) with xinerama

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
EndSection

Section "Files"
EndSection

Section "Module"
   Load  "record"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Fujitsu Siemens"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
    Option         "Primary"    "True"
EndSection

Section "Monitor"
  Identifier     "Monitor1"
  VendorName     "Proview"
  HorizSync       28.0 - 33.0
  VertRefresh     43.0 - 72.0
  Option         "RightOf" "Monitor0"
  Option         "Primary"    "False"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
        Modes           "1280x1024"
        Virtual          2560 1024
    EndSubSection
EndSection

Section "ServerFlags"
  Option    "Xinerama" "true"
EndSection