Instructions
Open your web browser and navigate to the Xbox 360 Media Download Center page (see Resources).
Click the link that corresponds to the operating system your Windows Media Center PC uses. This will download setup software, which you should save to your desktop.
Double-click the file you saved to your desktop and follow the step-by-step instructions to install the Xbox 360 Media Center support files.
Stop when the PC software's setup gets to the point where you need to input an eight-digit setup key.
Turn on your Xbox 360 and navigate to the "Media" tab.
Select the "Media Center" button at the bottom of the screen.
Write down the eight-digit setup key that the Xbox 360 provides you. Go back to your PC and input that key. The Xbox 360 and your Media Center PC will now connect to each other.