If you wish to purchase Halo for the PC and want to play the Co-Op campaign like the XBOX version, do not even waste your money. It is not an option. As a side note, the rendering speed is very poor, at best. The sound stutters often and skips dialog in the rendered cut scenes. So, unless you wish to play single player campaign or online multiplayer at 800×600, it is best to wait for patches to fix the problems. Your results may vary. However, feel free to wander around the net and lurk on forums to see if anyone else is having the same issues.