I also struggled with getting my Sony VGN-CS110E running Windows Vista Home Premium to display to my 40" Samsung HDTV correctly.
The first thing I tried was to go into the Vaio Control Center and checked the box "Change the external display detection method" in the External Display Detection Setting. This allowed a small desktop screen on the TV to appear in the center of the TV screen. The resolution setting was correct, but a huge border on the screen was just black. Worse, it only worked as an extended desktop since trying to set the TV as a clone or the primary monitor still failed to work.
Thinking I was on the right track though, I did a bit more fiddling around with settings but nothing helped.
Finally I disabled the Vaio Event Service from running at startup. Once I disabled that in msconfig and rebooted, the TV showed the desktop at full screen in the correct resolution and can now be used as the primary monitor. To get this to work correctly, I also had to set the TV as the main monitor in the Vista Display Settings control panel.
So it is finally working, and I believe I’ll contact Sony to find out what they have to say since this issue seems to be rather common and is caused by their software. Anyway, I just wanted to share my experience on this in case anyone finds it helpful.