http://www.infobarrel.com/How_to_Use_a_Laptop_to_Connect_Xbox_360_to_Xbox_Live
published November 25, 2008
How to Use a Laptop to Connect Xbox 360 to Xbox Live
by Jorge
Bridging your Laptop Internet Connection to Replace Xbox 360 Wireless Adapter
This video tutorial is an alternative method to connect your Xbox 360 to Xbox Live without having to buy the Xbox 360 Wireless Adapter. We will be using a computer (preferably a laptop) to replace needing an Xbox 360 wireless adapter. With this method we will need either a laptop or a PC running Windows right beside your Xbox 360 as well as an Ethernet wire. Your PC will need to have a wireless internet connection to your router.
Once you have everything above in order, follow this simple tutorial to bridge your PC's wireless connection and share it with your Xbox 360 so you can connect to Xbox Live.