Robin,
My first recommendation to you is to stop using Windows Firewall on the one notebook computer as it is pretty much garbage and not worth much in the way of protection. The AVG Pro and Zone Alarm are both good firewalls. I would put Zone Alarm on the notebook and stick with it, then let Spybot S & D fix the issue, then you don't have to worry about it. If you have a computer that is not on a network, but does access the internet, you still want to fix it if it is your only firewall. It will not effect how your network operates. The only thing this fixes is stopping inbound requests that you DID NOT initiate. Let Spybot fix it, then let your other firewall protect you. You're much better off that way. Hope this helps, if not, post again and I'll try to explain a bit better.
Tony