Instructions
Turn on both the console and the Windows XP laptop.
Connect your Windows XP laptop to your wireless Internet.
Connect your Xbox 360 to your laptop via Ethernet cable, then wait for a "Local Area Network" notification to appear in your computer's taskbar. The notification indicates your computer and Xbox 360 are networked.
Right-click the "Local Area Network" icon in the taskbar, then click "Open Network Connections." This allows you to view your computer's network connections, including its wireless Internet connection and local area network connection between it and the Xbox 360.
Hold down the CTRL key on your laptop's keyboard, then click once on both the wireless Internet connection and the "Local Area Network." Notice that both connections are selected. Release the CTRL key.
Click the "Advanced" drop-down menu on the top of the "Network Connections" window, then select "Bridge Connections." The Windows XP laptop will take a few moments to set up the network bridge. Afterward, your Xbox 360 will be able to share your computer's wireless Internet connection.