Home Firewall: Opening ports for XBox to PC communications

From XBox help and support: Xbox 360: Firewall ports that you must open when you connect an Xbox 360 console to a Windows Media Center-based computer. These rules are applied on a local (home) router between the XBox and the PC.

A separate article on Firewall rules that need to be modifed on the Windows Media PC itself (assumes ICF or otehr PC based Firewall).