[Paul]

Dunno if anyone has posted this but a useful tool to check on what ports are active on your PC at any one time
CurrPorts
CurrPorts Download

CurrPorts displays the list of all currently opened TCP/IP and UDP ports on your local computer. For each port in the list, information about the process that opened the port is also displayed, including the process name, full path of the process, version information of the process (product name, file description, and so on), the time that the process was created, and the user that created it.
In addition, CurrPorts allows you to close unwanted TCP connections, kill the process that opened the ports, and save the TCP/UDP ports information to HTML file , XML file, or to tab-delimited text file.
CurrPorts also automatically mark with pink color suspicious TCP/UDP ports owned by unidentified applications.
System Requirements
This utility works perfectly under Windows NT, Windows 2000, and Windows XP. If you want to use this utility on Windows NT, you should install psapi.dll in your system32 directory.
You can also use this utility on previous versions of Windows (Windows 98/ME), but in these versions of Windows, the process information for each port won't be displayed.