I can't find it
Start->Accessories right click on "Command prompt", in menu click "Run as Administrator" (on Windows XP you can just run it as usual), run netstat -anb
then look through output for your program.
BTW, Skype by default tries to use ports 80 and 443 for incoming connections.
You can also run netstat -anb >%USERPROFILE%\ports.txt
followed by start %USERPROFILE%\ports.txt
to open port and process list in a text editor, where you can search for information you want.
If you want to be really fancy, download TCPView from sysinternals
TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on your system, including the local and remote addresses and state of TCP connections. On Windows Server 2008, Vista, and XP, TCPView also reports the name of the process that owns the endpoint. TCPView provides a more informative and conveniently presented subset of the Netstat program that ships with Windows.