Instructions
Plug the Ethernet cable into both the laptop and the Microsoft Xbox 360.
Right-click the "Network" icon on the right side of your task bar, and click "Network and Sharing Center."
From the Network and Sharing Center window, select "Manage Network Connections" on the left side of the window.
In the Network Connections window, select both the "Local Area Connection" and the air card's Internet connection by holding down the "Ctrl" key while clicking on each.
Once both icons are highlighted, right-click on either of them and select "Bridge Connection." This may take a few minutes, but this is normal.
Turn your Xbox 360 on and navigate to the Xbox 360 "Settings." From there, go to the "Network Settings."
From the Network Settings on the Xbox 360, select "Test Xbox Live Connection." The Xbox will handle the rest of the setup.