Constant IP Popup in Norton Firewall/AV

We have WinXP Pro and Norton Internet Security Professional installed with Linksys WRT54G Router since we are connected to a cable modem. One computer constantly having pop-up requests from several IP trying to enter ports 1026 – 8, 2745, 3127, and 6129 to name a few. From MS DOS screen, I tried pinging several IP, but no id appears. My question is how can I check the ports or find a system file that reports such attempts so I can close the ports. The other computer has no problems and they both are identical. Only difference is that one has the Logitech webcam. (Not in use unless we use Netmeeting)