Our thanks for Rhinoman pointing out use of the netstat -an utility in one of his responses, I forgot where he did this but its very helpful. The url above will take you to Microsoft Knowledge base article explaining about netstat and how to use its output with task manager to identify who is using the port or ports. So by entering netstat -ano you also get the process identifier, bring up the task manager and see who it belongs to. Read the article though, its good to always go to a reference.

Operating System:Windows XP Pro
Product Name:ZoneAlarm Pro
Software Version:3.7