Comment 29 for bug 82312

thanks, the line
 Option "ConnectedMonitor" "dfp, crt, tv"
did help eventually!

After I got a working single monitor display going and this line in the Screen section, the nvidia-settings picked it up and configured it (first with the screens in the wrong order, causing the login screen to appear on the TV, but that's quite easily fixed)

After some cleaning up, it now looks like this:

Section "ServerLayout"
    Identifier "Layout0"
    Screen 0 "Screen0" RightOf "Screen1"
    Screen 1 "Screen1" 0 0
    InputDevice "Keyboard0" "CoreKeyboard"
    InputDevice "Mouse0" "CorePointer"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier "Monitor1"
    VendorName "Unknown"
    ModelName "Nvidia Default Flat Panel"
    HorizSync 29.0 - 65.0
    VertRefresh 0.0 - 60.0
    Option "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: builtin, VertRefresh source: builtin
    Identifier "Monitor0"
    VendorName "Unknown"
    ModelName "TV-0"
    HorizSync 28.0 - 33.0
    VertRefresh 43.0 - 72.0
    Option "DPMS"
EndSection

Section "Device"
    Identifier "Videocard0"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "GeForce4 420 Go"
    BusID "PCI:1:0:0"
    Screen 0
EndSection

Section "Device"
    Identifier "Videocard1"
    Driver "nvidia"
    VendorName "NVIDIA Corporation"
    BoardName "GeForce4 420 Go"
    BusID "PCI:1:0:0"
    Screen 1
EndSection

Section "Screen"
    Identifier "Screen0"
    Device "Videocard0"
    Monitor "Monitor1"
    DefaultDepth 24
    Option "metamodes" "DFP: 1400x1050 +0+0"
    SubSection "Display"
        Depth 24
        Modes "1400x1050"
    EndSubSection
EndSection

Section "Screen"
    Identifier "Screen1"
    Device "Videocard1"
    Monitor "Monitor0"
    DefaultDepth 24
    Option "metamodes" "TV: 800x600 +0+0"
    SubSection "Display"
        Depth 24
        Modes "800x600" "640x480"
    EndSubSection
EndSection