Most HDTVs have built-in options for letterboxing vs stretching/zooming 4:3(standard def) content when displayed on a 16:9(high def) screen. Only downside would be that if you are using the setting in the TV itself, it is going to either always be on or always off, no quick switching with a button on the remote, it's all or nothing at that point. Heck, even my Toshiba HDTV from 2001 had that setting, I'd be surprised if your TV doesn't have it, it's almost as standard as contrast and brightness controls anymore.