Watching Ports with Port Reporter
Port Reporter is another cool tool from Redmond. It runs as a service in Windows XP/2003 (and also in Windows 2000 but with less functionality) and records information about which TCP and UDP ports are active on your system. Port Reporter also tells you the Windows processes that are using these ports and the security context under which each process is running. You can use Port Reporter to monitor port usage for security reasons and for troubleshooting network connectivity problems.