You might also post the brand and model, along with the sorce for the
signal. What is the HD source, what resolution, and what do you mean
by
switching to widescreen. All HD is widescreen.

It's a 30" Philips widescreen. (model: 30PW862H)

As for the switching; my particular cable provider only offers a couple
channels in HDTV, so I haven't made the switch yet. So, when the video
game console is utilized (Xbox), which is hooked up via the
'High-definition pack', 480p mode is engaged -- and it's full screen.
Whereas the digital cable is set at 4:3 because I like the resolution
better.