[KJ44]

I run two monitors of different resolutions on an nVIDIA 6600, as two separate X screens. You might find my (edited for space) xorg.conf useful.

                                                                    

Section "ServerLayout"
    Identifier     "Layout[all]"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" RightOf "Screen0"
    InputDevice    "Keyboard[0]" "CoreKeyboard"
    InputDevice    "Mouse[1]" "CorePointer"    
    Option         "Clone" "off"               
    Option         "Xinerama" "off"            
EndSection                                     
                                                                                                                                             
Section "Files"                                                                                                                              
    InputDevices      "/dev/gpmdata"                                                                                                         
    InputDevices      "/dev/input/mice"                                                                                                      
    FontPath        "/usr/share/fonts/misc:unscaled"
    <snip>                                                                                                                                                                                 
EndSection                                                                                                                                   

Section "Module"
    Load           "glx"
    Load           "type1"
    Load           "extmod"
    Load           "dbe"   
    Load           "freetype"
EndSection                   

Section "ServerFlags"
    Option         "AllowMouseOpenFail" "on"
    Option         "ZapWarning" "on"        
    Option         "Xinerama" "0"           
EndSection                                  

Section "InputDevice"
    Identifier     "Keyboard[0]"
    Driver         "kbd"        
    Option         "Protocol" "Standard"
    Option         "XkbLayout" "us"     
    Option         "XkbModel" "microsoftpro"
    Option         "XkbRules" "xfree86"     
EndSection                                  

Section "InputDevice"
    Identifier     "Mouse[1]"
    Driver         "mouse"   
    Option         "Buttons" "7"
    Option         "Device" "/dev/input/mice"
    Option         "Name" "Microsoft IntelliMouse Optical"
    Option         "Protocol" "explorerps/2"              
    Option         "Vendor" "Sysp"                        
    Option         "ZAxisMapping" "4 5"                   
EndSection                                                

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Dell"    
    ModelName      "DELL 1704FPT"
    HorizSync       30.0 - 81.0  
    VertRefresh     56.0 - 76.0  
    Option         "DPMS"        
    Option         "PreferredMode" "1280x1024"
EndSection                                    

Section "Monitor"
    Identifier     "Monitor1"
    VendorName     "Samsung" 
    ModelName      "SAMSUNG LE22S86BD"
    HorizSync       30.0 - 81.0       
    VertRefresh     60.0 - 75.0       
EndSection                            

Section "Device"
    Identifier     "Videocard0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 6600"
    BusID          "PCI:1:0:0"
    Screen          0
EndSection

Section "Device"
    Identifier     "Videocard1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "GeForce 6600"
    BusID          "PCI:1:0:0"
    Screen          1
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Videocard0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "TwinViewXineramaInfoOrder" "DFP-0"
    Option         "metamodes" "DFP: 1280x1024 +0+0"
    SubSection     "Display"
        Depth       24
        Modes      "1280x1024"
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Videocard1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "TwinView" "0"
    Option         "TwinViewXineramaInfoOrder" "CRT-0"
    Option         "metamodes" "CRT: 1680x1050 +0+0"
EndSection

Section "Extensions"
    Option         "Composite" "on"
EndSection