I'm currently converting avi 720x400 to mpg.. i want to keep that widescreen aspect... so I chose to convert it to 720x400...will that work as vcd?
Yup, it'll work, however... You'll be making a xVCD and not all players can play that. I'd suggest converting about 10 secs or so and then trying burning onto a CD-RW to see if your stand-alone can play it. However, if you want wide screen, be sure to choose a 16:9 (or whatever) widescreen ratio in the encoder you're using.
preferably, i would make xsvcd. and i would put it to 720x480 resolution. but the pic will still be in 720x400. xvcd is fine too. if you put it at 720x400, which is an illegal height, it won't play properly. you might want to increase the bitrate, rather than the default 1150kbps, as you're encoding at a larger resolution.