You might need something like this:
Section "Device"
Identifier "Videocard0"
Driver "nvidia"
VendorName "Chaintech"
BoardName "nVidia GeForce 4 MX 440"
Option "RenderAccel" "1"
# TV Out Setup
Option "TVStandard" "NTSC-M"
->>> Option "TVOutFormat" "SVIDEO"
Option "TVOverScan" "0.45"
EndSection