Best firewall: zonealarm. As soon as that is ready, turn the windows firewall off, it is crap.
Avast is a very good antivirus program, but rather heavy on resources; AVG is almost as good, but much easier on the computer. Comes in handy when you have a hungry system like vista.
A most useful tiny little program is Winpatrol. It will come up with an alert every time there is anything trying to set itself up as an automatic startup program. Invaluable to stop all kinds of advertising, datamining and other unwanteds that are not in the chapter with viruses, trojans, worms and the likes.
Adaware is also very useful.
Get rid of anything to do with norton and macaffee.
Unless you have 5gig of ram or more, get rid of vista and go back to xp.