Works on my card, with new (4363) driver!
GeForce4 MX440, NV17 encoder
With the new 4363 driver the TVOverScan function works nicely, I can use all values between 0.0 and 1.0:
"0.0": gives a really small picture (wide black borders)
"1.0": gives full overscan (no black borders at all).
"0.5": seems to give the picture as with the old (4349) drivers (i.e. slight black borders).
Thanks for fixing the OverScan bug, NVIDIA!