So it just might be possible that you (iwaschosen) were clicking on the Halo icon, not Halo CE

Re: HALO CE on vista problems
 

I know this is an old thread, so if you have already found a solution then ignore this post, but if you are still in the search for a solution then try this.

1) Go to control panel (easy access in start menu)
2) Select hardware and sound
3) Scroll down until you find your video card. Since you are using an NVIDIA GeForce, you should find an icon with the NVIDIA LOGO and it will say NVIDIA CONTROL PANEL. Click on this icon.
4)The first page you see will be called Adjust Image settings with preview. There should be a green NVIDIA logo spining around and a few options and a slider bar to select under the logo. The three options you should see are
A)let the 3d application decide
B)Use the advanced image settings
C)Use my preferance emphasizing: (will either be set to quality or performance depending on where you have the slider.)
5) Select Let the 3d application decide.

This should fix the problem you are having.