Ok, ive done that now. Its half fixed it. When I open Halo now, it goes past
the intros, but its all white and jittery, i go into the game and i can make
out white shapes and outlines and the sound still plays fine and i can look
around and see more white shapes and outlines. So how do i fix this?

Oh, and when installing DirectX, I open it and choose install, and when it
says something like 'Click next to install, it may take a few minutes' i
click it and it instantly says finished. So im thinkin maybe its not
installing it properly?