Norton is a pretty good antivirus program, but it's hard on computer resources. My aunt uses Symantec Client Security, with the firewall and stuff and it works okay.
I use ZoneAlarm (the free version) for firewall protection along with AVG Free Edition for antivirus and it works just as well as Norton, but uses much less resources. Both versions can be downloaded from the internet, and probably like 30 MB (guess) for both or something won't take long on an average broadband connection.
- AVG Antivirus
ZoneAlarm can be downloaded here
and many other places.