goto... start/run then type cmd or command. Then type ipconfig/all. find your DNS server IP and write it down. Then type this IP into an browser(I.E.,mozilla, etc). This should bring up your router configuration page. There is usually settings in there dealing with ports after you get to the page.
It also may be your firewall... disable any firewalls you may have before you play.
"Power never takes a back step - only in the face of more power