Re: 360 and PC
If you have a Window's Live Gold account you can play some games on your PC versus people playing on their Xboxes. You have to pay for a Gold account and I don't know all the games that allow that kind of connectivity. Gears of War is one of them though.
Intel Quad 6600, Asus P5N-E SLI, GeForce GTX 560 1GB, 6GB RAM, 500GB HDD, Zalman 9700NT, X-Fi Xtreme Gamer, 650 watt PSU