so now I finally got it working. Some problems might occur stupid and are not really backtrack specific ( more Linux general ) but i hope you dont mind me writing down my solution for the problem.
So my first mistake I tried to get it running with "nv" driver. I should have installed the proper "nvidia" driver. you can download the files you need at nvidias homepage...
next thing i read on some other forums (mostly ubuntu forums) about setting up the xorg.conf with xinerama. after several tries i finally got it working
once again I own a NVIDIA GeForce Go5200 FX. I tried to use an external monitor (Samsung Syncmaster 755DFX) besides my laptop interneal screen 
Code:
Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0" 0 0
Screen 1 "Screen1" RightOf "Screen0"
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
InputDevice "Synaptics Touchpad"
InputDevice "cursor" "SendCoreEvents"
InputDevice "stylus" "SendCoreEvents"
InputDevice "eraser" "SendCoreEvents"
InputDevice "pad"
EndSection
Section "Files"
RgbPath "/usr/lib/X11/rgb"
EndSection
Section "Module"
Load "dbe"
Load "extmod"
Load "type1"
Load "freetype"
Load "glx"
EndSection
Section "ServerFlags"
Option "Xinerama" "1"
EndSection
Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection
Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "HorizEdgeScroll" "0"
Option "SHMConfig" "on"
EndSection
Section "InputDevice"
Identifier "cursor"
Driver "wacom"
Option "Device" "/dev/input/wacom"
Option "Type" "cursor"
Option "USB" "on"
EndSection
Section "InputDevice"
Identifier "stylus"
Driver "wacom"
Option "Device" "/dev/input/wacom"
Option "Type" "stylus"
Option "USB" "on"
Option "Mode" "Relative"
# Option "Mode" "Absolute"
Option "PressCurve" "50,0,100,50"
# Option "TopX" "0"
# Option "TopY" "0"
# Option "BottomX" "104204" # Versuch wegen DualScreen (nicht geklappt)
# Option "BottomX" "54204"
# Option "BottomY" "31750"
# Option "TVResolution" "1920x1200,1600x1200"
# Option "Twinview" "horizontal"
# Option "ScreenNo" "0"
EndSection
Section "InputDevice"
Identifier "eraser"
Driver "wacom"
Option "Device" "/dev/input/wacom"
Option "Type" "eraser"
Option "USB" "on"
Option "Mode" "Absolute"
Option "ScreenNo" "0"
Option "TVResolution" "1920x1200,1600x1200"
EndSection
Section "InputDevice"
Identifier "pad"
Driver "wacom"
Option "Device" "/dev/input/wacom"
Option "Type" "pad"
Option "USB" "on"
EndSection
Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "kbd"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "ch"
Option "XkbVariant" "de"
EndSection
Section "Monitor"
# HorizSync source: edid, VertRefresh source: edid
Identifier "Monitor0"
VendorName "Unknown"
ModelName "LPL"
HorizSync 30.0 - 75.0
VertRefresh 60.0
Option "DPMS"
EndSection
Section "Monitor"
# HorizSync source: unknown, VertRefresh source: unknown
Identifier "Monitor1"
VendorName "Unknown"
ModelName "EIZO L885"
HorizSync 0.0 - 0.0
VertRefresh 0.0
Option "DPMS"
EndSection
Section "Device"
Identifier "Videocard0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce Go5200"
BusID "PCI:1:0:0"
Screen 0
EndSection
Section "Device"
Identifier "Videocard1"
Driver "nvidia"
VendorName "NVIDIA Corporation"
BoardName "GeForce Go5200"
BusID "PCI:1:0:0"
Screen 1
EndSection
Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
Option "TwinView" "0"
Option "metamodes" "DFP: 1024x768 +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection
Section "Screen"
Identifier "Screen1"
Device "Videocard1"
Monitor "Monitor1"
DefaultDepth 24
Option "TwinView" "0"
Option "metamodes" "CRT: nvidia-auto-select +0+0"
SubSection "Display"
Depth 24
EndSubSection
EndSection