If using vegas or AE just select the 720p preset. Other than that: 1280x720, at 30frames, pixel aspect ratio 1,00000 (square).
And force it to using a high bitrate (as mentioned above, 3M/3000kbps or more)
720p is 16:9 widescreen.[/b]
holy christ schrotti, where were u when i had so many questions about vegas 8? Damn this would have helped me months ago :P thanks for the tips <3