Oh god. I just hope somebody out there is deriving some amusement from this thread.
First, @post-it:
1) "CBR" stands for
"Chaotic Bad Raptor" "
Constant Bit Rate". Get it right.
2) If the bitrate is too low with ANY lossy codec, it'll look like garbage. This is hardly specific to XviD.
3) I'd love to know how constant bit rate works "better" than constant quantizer or 2-pass VBR. Especially for videos that contain both really low-motion scenes and really high-motion ones.
@Brittanysama: if you really want as close to "what you see is what you get" as is possible with XviD, do a "Twopass - 1st pass" run with "Full quality first pass" checked, "Discard first pass" unchecked, and all minimum quantizers set to 2. (You could even do 1, but all reports are that that makes much bigger files without looking noticeably different.)
Actually, come to think of it, single pass with "Target quantizer" set to 1 (which is what I think AaronAMV was suggesting, but he just wasn't very clear about it) might also work, but I've never tried it.
Also, it never hurts to

so that we can tell you if you have a problem there.
@Sentrix: using an .MP4 container doesn't preclude using XviD; it would have been more accurate to say "use
x264 using Zarxgui". (Though using Zarxrax's GUI might, seeing as how it's got "x264" in the name, but I've never seen it, so I don't know.)