Aqui está o meu xorg.conf, sem comentários, para um laptop com um chip Nvidia. Você pode começar daqui e editá-lo.
Você também tenta executar a ferramenta nvidia-xconfig, mas não cria configurações adequadas para os servidores xorg modernos. Mas você pode cortar e colar a parte do driver e adicioná-la a essa.
Section "Files"
FontPath "/usr/share/fonts/misc"
FontPath "/usr/share/fonts/Type1"
FontPath "/usr/share/fonts/TTF"
FontPath "/usr/share/fonts/75dpi"
FontPath "/usr/share/fonts/100dpi"
FontPath "/usr/share/fonts/aquafont"
FontPath "/usr/share/fonts/urw-fonts"
FontPath "/usr/share/fonts/corefonts"
FontPath "/usr/share/fonts/sgi-fonts"
FontPath "/usr/share/fonts/cronyx"
FontPath "/usr/share/fonts/cyrillic"
FontPath "/usr/share/fonts/essays1743"
FontPath "/usr/share/fonts/freefonts"
FontPath "/usr/share/fonts/freefont-ttf"
FontPath "/usr/share/fonts/libertine-ttf"
FontPath "/usr/share/fonts/intlfonts"
FontPath "/usr/share/fonts/terminus"
FontPath "/usr/share/fonts/ttf-bitstream-vera"
FontPath "/usr/share/fonts/unifont"
FontPath "/usr/share/fonts/dejavu"
FontPath "/usr/share/fonts/mplus-outline-fonts"
FontPath "/usr/share/fonts/OTF"
FontPath "/usr/share/fonts/Speedo"
FontPath "/usr/share/fonts/stix-fonts"
FontPath "/usr/share/fonts/tengwar-fonts"
FontPath "/usr/share/fonts/thaifonts-scalable"
FontPath "/usr/share/fonts/unfonts"
FontPath "/usr/share/fonts/urwvn-fonts"
FontPath "/usr/share/fonts/vdrsymbols-ttf"
FontPath "/usr/share/fonts/liberation-fonts"
FontPath "/usr/share/fonts/arphicfonts"
FontPath "/usr/share/fonts/culmus"
FontPath "/usr/share/fonts/droid"
FontPath "/usr/share/fonts/efont-unicode"
FontPath "/usr/share/fonts/farsi-fonts"
FontPath "/usr/share/fonts/mathematica-fonts"
FontPath "/usr/share/fonts/mikachan-font-ttf"
FontPath "/usr/share/fonts/opendesktop-fonts"
FontPath "/usr/share/fonts/proggy-fonts"
FontPath "/usr/share/fonts/unifont"
FontPath "/usr/share/fonts/webby-fonts"
EndSection
Section "Module"
Load "dbe"
SubSection "extmod"
Option "omit xfree86-dga"
Option "omit apm"
EndSubSection
Load "glx"
Load "v4l"
EndSection
Section "ServerFlags"
Option "blank time" "5" # 10 minutes
Option "standby time" "10"
Option "suspend time" "20"
Option "off time" "30"
EndSection
Section "DRI"
Mode 0666
EndSection
Section "Monitor"
Identifier "MetaMonitor"
Option "DPMS"
EndSection
Section "Device"
Identifier "Nvidia"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "Quadro FX 2800M"
EndSection
Section "InputClass"
Identifier "synaptics"
MatchIsTouchpad "on"
Driver "synaptics"
#Option "SHMConfig" "on"
Option "VertTwoFingerScroll" "on"
EndSection
Section "Screen"
Identifier "Screen1"
Device "Nvidia"
Monitor "MetaMonitor"
DefaultDepth 24
Option "TwinView" "1"
Option "metamodes" "DFP-0: nvidia-auto-select +0+0, DFP-1: nvidia-auto-select +1920+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "ServerLayout"
Identifier "Main Layout"
Screen 0 "Screen1" 0 0
Option "Xinerama" "0"
EndSection