You mean Halo 2 because of the DirectX 10 requirement. That is also the case for GTA IV. It is based of the DirectX 10 engine which of course is not on XP so that forces you into having to have Vista running. I played GTA IV for a while and I never really got into it. It was poorly written and from a graphical perspective on the PS3 it wasn't very jaw dropping. I've seen the Xbox360 version and it looked worse then the PS3 version. In short I'm saying your not missing anything.