I just wanted to mention that you might be dissatisfied with the quality of your TV as a computer monitor. I haven't seen any TV that made a good computer monitor, mostly because of super low resolution (given how huge the display is). A 42" wide screen display with a proper dot-per-inch ratio (to be around the average of a real computer dispaly) would have a resolution like 3500 x 2200. Your TV will certainly not.
So in summary, you're going to have the same resolution of a 17" display, but blown up to 42", rather than a an actual higher resolution.
That's why when the 30" Apple display first came out, everyone made a big fuss about, not because of how big it was, but because of the incredible resolution (2560 x 1600).