Instructions
Turn on the computer and Xbox 360. Select "My Xbox" on the Xbox console and click "Windows Media Player."
Follow the on-screen instructions until you are presented with an eight-digit Media Center setup key. Write down this key and keep it handy.
Launch Windows Media Center. Click "tasks" and then select "add extender" from the menu. Complete the brief set of on-screen instructions until asked for the setup key.
Enter the eight-digit Media Center key from the Xbox 360 when prompted, and complete the short extender setup.
Check that your computer's firewall settings are configured to allow Xbox 360 to connect to the computer from which you are running Windows Media Player. Once complete, the Windows Media Center interface will appear on the television connected to your Xbox 360 console.