I tested a friends computer at www.grc.com (Steve Gibson's Shields Up!). According to the port scan test, he has port numbers 135 (RPC?) and 1024 (DCOM?) wide open, whilst my computer is running in full 100% Stealth mode. I'm running XP Professional with ZoneAlarm Personal, he's running XP Home with McAfee firewall.
He hasn't any problems with "computer bugs" and he's has all the latest Windows updates installed.
Is this an operating system issue, a firewall problem or something else?
I'd welcome your feedback.