I don't know if this has something to do with this, but I found a paragraph in a review that has a similar problem.
, some lines above the SCREENSHOTS title:
Note that you can always scale down your video card but you can?t scale up. Check your video card?s documentation to determine witch version of DirectX / pixel shaders it supports. If, for example, your card supports PS2.0, you can choose to compromise many of Halo?s effects by forcing it to run PS1.1. However, if your card supports PS1.1, you can?t force it to PS2.0 ? this is actually happening in hardware, not in software.
Note that the '
s were replaced with ?