QUOTE(Venom1188 @ Dec 14 2007, 08:07 PM)
I have my 360 connected to my 19" widescreen monitor via VGA cable.
What is the native resolution of your monitor, and what resolution is the Xbox outputting? If your monitor's resolution is 1680x1050 (the most common resolution for that size), and your Xbox is outputting at 1280x720, your monitor will be (poorly) upscaling the image, and since Halo 3 has visible jaggies
anyway, the problem will only be compounded.
Unfortunately the Xbox 360 doesn't play nice with non-16:9 widescreen monitors; people have been begging for 16:10 support for a long time, but to no avail. There are standalone scalers on the market that will intelligently convert your 720p image to 1050p, eliminating the first wave of jaggies, but unless you're made of money you're better off finding another monitor. Sorry for the bad news.