Thanks to optiplex for posting this in the back page forums.
Microsoft has identified a potential incompatibility between Halo for PC and Windows XP SP2, on certain high-end video cards, which causes Halo to exit silently to the desktop immedately after launching the program, before the logo movies play. Systems which can get beyond that point are unaffected by this problem, and will not benefit from this fix.
Note: You must patch Halo to the latest version (1.04) before applying this fix. Please download Halo 1.04 from: (below)
Microsoft has only seen this problem on computers with an nVidia GeForce 5900, 5950, or ATI X800 video card, and only on certain driver versions, including the nVidia drivers included by default in new installations of Windows XP SP2.
Get more info at the link below.