Halo 2 PC is no reason to run out and upgrade to Vista, which is one thing you can be sure of. I don't know if Microsoft was trying to get more people to buy Windows Vista or what, but just don't. This makes the cost for most users far more than just the $50 to buy Halo 2, but also a Windows Vista upgrade. Wait for a good game that actually takes advantage of DirectX10 before you do that.