u can try the following
go to
http://www.grc.com/x/ne.dll?rh1dkyd2this is a cool website, free, and tells u what ports are open and which one are closed, and which ones that are stealthy.. usually a firewall should help u close all ur ports and even make them undetectable by scanners
if u run the "All Service Ports", u can click on the red little square which represent ports and u can find out the number and what that port is usually used for.
again firewall makes all ports (usually) stealthy