4x3 to end up with 16x9, if you use 16x9, you'll get 2.35:1 big widescreen.

I'd keep it in 4'3, it will play fine, it isn't really worth all of the trouble to go through to "convert it" or basically "fake it" in 16:9, and since you shot video without having 16:9 in mind, I'm sure you will end up cutting alot out if you do letterboxing. Sometimes I wish I had a cam that did true 16:9, lol.

ive just asked a similar question

http://dvinfo.net/conf/showthread.php?t=111527

if your using vegas you can use pan and crop and there is a 16:9 in the drop down menu that will trim you footage without letterboxing

not sure about other software but i assume it will have a similar feature

ive figured if i render the file then crop the rendered file after its easier but it must degrade the quality slightly which is why i wondered if there was a way to do a batch of clips in the first render