GeForce 7800 GSOC with HDTV

I have a Sony KDF-E55A20 TV that I'm using as a computer monitor.

When I use an analog signal converter to convert my VGA output to Component,
it looks pretty good, but the picture doesn't fill the screen.

When I use a DVI to HDMI cable co connect the nVidia's DVI output to my TV's
HDMI input, it fills the whole screen, and the colors are much better,
however the screen is "pixilated" if that's the right word--if you've ever
seen an LCD screen set to a non-native resolution, you know what I mean.

I looked up the native resolution of the screen, and Sony claims it's 1366 x
768. When I try to set that as a custom resolution in ForceWare Release 90
(Version: 91.31 Release Date: June 23, 2006) it will not even test the
resolution, it just says "invalid resolution."



Here's Sony's specs on the TV:
Video
Native Resolution: 720p
Display Resolution: 1366 x 768
Vertical Size: +5 to -5
Vertical Center: +5 to -5

How can I make the software accept my custom resolution, and if I can get it
to accept it, will it solve the problem?