Instructions
Set Up the Ad-Hoc
Open the "Start" menu, followed by the "Control Panel," followed by the "Network and Sharing Center." In the Windows operating system, you open menu icons by left-clicking on them one time.
Click "Set up a New Connection."
Browse through the types of connections that you can create until you find the one for "Ad-Hoc." Click it, and select "Next." Type your desired name for your Ad-Hoc connection (it is important that you pick something you can remember, as you will need to know this name to connect your Xbox 360 to your computer). Leave the security type as "None" and click "Create." Close the Network and Sharing Center.
Connect with Your Xbox 360
Turn on your Xbox 360.
Select "My Xbox" from your Xbox 360's menu system.
Choose "System Settings" and select the "Network Settings" icon.
Open "Configure Networks," followed by "Wireless Mode."
Select "Scan for Networks." Select the name that you gave your Ad-Hoc connection in the previous section. Choose "Done." Your Xbox 360 is now connected to the Internet through your computer's Wi-Fi connection.