If you're on Windows then the built-in Firewall is "good enough" and for antivirus I'd suggest Grisoft's AVG antivirus -
http://www.grisoft.com/
Beware of Norton, it's very intrusive and sometimes has strange effects on people's systems.
If on a Mac or Linux (my current fave distro is Kubuntu) then you really don't need to worry about such things.