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Norton Internet Security includes a firewall and anti-virus. As with other firewalls Norton's can sometimes become very unhelpful at inconvenient times, e.g. downloading updates to AVG or anti-spyware programs in exactly the situation when you wouldn't subscribe to an update by entering credit card details.

Effectively what has happened is that the system hooks are still in place, but the user interface is no longer asking for permission to allow a new program to open a connection. Attempting to uninstall via Add/Remove Programs gives a misleading message about needing a Norton administrator password; it also refuses point blank to uninstall in safe mode.

The trick is simply to go to Control Panel > Services and stop all Symantec or Norton services and then uninstall.

As to whether a firewall is wise for a home computer - yes, if you are using a USB ADSL modem and connected for long stretches of time; if you are connecting through a router, the hardware firewall may be all you need. Windows XP firewall is probably sufficient and adapted to home networking, unless you want greater control over which programs have access.