Instructions
Obtain Your Computer's MAC Address
Open your "Start" menu and click "Run." If you don't see it, press and hold the "Windows" key on your keyboard, then press "R."
Type in "cmd" and then press "Enter" to open the command prompt.
Type "ipconfig/all" and press "Enter." Write down the MAC address listed; it will be labeled "Physical address" and have 12 digits.
Configure the Xbox 360 with an Alternative MAC Address
Go to "My Xbox" in your console and select the "System Settings" panel.
Select "Network Settings," then "Configure Network."
Select the "Additional Settings" tab and open "Advanced Settings."
Select "Alternate MAC Address" and enter your computer's MAC address. When you've finished, select "Done."
Select "Done" again and then press "B" on your controller. Choose to test your connection to see if the connectivity issue has been resolved.