Randy, it sounds like you want to use the HT200DM on a 4:3 ratio screen... is that right?
I think most people with this projector will prefer a 16:9 ratio screen, where 4:3 video is formatted by the projector to sit in the center, with black bars on the edges. Aside from the natural match to DVD movies and HDTV with a 16:9 ratio screen, the other reason is refresh rate. The DLP chip runs at a slower refresh rate in 4:3 (800 x 600) mode, compared to 16:9 (848 x 480) where some of the mirrors are shut down. The faster refresh rate in 16:9 mode means slightly better performance, and fewer image artifacts.
So, in theory, you'll get a better 4:3 image with this projector if you use a 16:9 ratio screen, and keep the projector in 16:9 mode full-time, with your 4:3 material formatted in black bars.
I know that some people prefer to run 4:3 video on a big 4:3 screen, with 16:9 "letterboxed" in the middle. It's nice for computer games and old movies. I just thought I'd mention the performance trade-offs when running this particular projector in the full 800 x 600 mode. It's a subtle effect, you may not notice the difference… but I think I can see a smoother image in the 848 x 480 mode.
I don't know if this helps or not. Let me know if there's any other info I can give you. I just got one of these projectors recently and I've been fooling around with it.