Ths is the Dual Head xorg.conf file for my Sony Vaio VGN-A170P laptop:

# Xorg configuration for dual head display on Vaio VGN series
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Section "ServerLayout"
Identifier     "DualHead"
Screen         "Screen1" LeftOf "Screen0"
Screen	       "Screen0"
InputDevice    "Mouse0" "CorePointer"
InputDevice    "Keyboard0" "CoreKeyboard"
Option	       "Xinerama" "on"
EndSection
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Section "Files"
RgbPath      "/usr/X11R6/lib/X11/rgb"
FontPath     "unix/:7100"
EndSection
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Section "Module"
Load  "dbe"
Load  "extmod"
Load  "fbdevhw"
Load  "glx"
Load  "record"
Load  "freetype"
Load  "type1"
Load  "dri"
EndSection
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Section "InputDevice"
Identifier  "Keyboard0"
Driver      "kbd"
Option	    "XkbModel" "pc105"
Option	    "XkbLayout" "us"
EndSection
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Section "InputDevice"
Identifier  "Mouse0"
Driver      "mouse"
Option	    "Protocol" "IMPS/2"
Option	    "Device" "/dev/input/mice"
Option	    "ZAxisMapping" "4 5"
Option	    "Emulate3Buttons" "yes"
EndSection
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Section "Monitor"
Identifier   "Monitor0"
VendorName   "Monitor Vendor"
ModelName    "LCD Panel 1920x1200"
HorizSync    31.5 - 90.0
VertRefresh  60.0 - 60.0
Option	    "dpms"
EndSection
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Section "Monitor"
Identifier   "Monitor1"
VendorName   "Samsung"
ModelName    "SyncMaster 153v"
HorizSync    31.5 - 90.0
VertRefresh  60.0 - 60.0
Option      "dpms"
EndSection
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Section "Device"
Identifier  "Videocard0"
Driver      "ati"
VendorName  "ATI"
BoardName   "ATI Radeon Mobility 9700"
Screen       0
BusID       "PCI:1:0:0"
EndSection
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Section "Device"
Identifier  "Videocard1"
Driver      "ati"
VendorName  "ATI"
BoardName   "ATI Radeon Mobility 9700"
BusID       "PCI:1:0:0"
Screen       1
EndSection
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Section "Screen"
Identifier "Screen1"
Device     "Videocard0"
Monitor    "Monitor0"
DefaultDepth     24
SubSection "Display"
Viewport   0 0
Depth     24
Modes    "1920x1200"
EndSubSection
EndSection
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Section "Screen"
Identifier "Screen0"
Device     "Videocard1"
Monitor    "Monitor1"
DefaultDepth     24
SubSection "Display"
Viewport   0 0
Depth     24
Modes    "1024x768"
EndSubSection
EndSection
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Section "DRI"
Group        0
Mode         0666
EndSection