I have tried several but ended up with Live One Care. Obviously, you will want to have antivirus, antispyware, and a firewall. This product gives you all three. I do like Zone Alarm's firewall best though and have opted to keep their free firewall in addition to my Live One Care.

So here is the thing with free vs. a bought product.

1) Antivirus: they require very frequent updates. Hackers are constantly developing new viruses. Some do it for sport others do it for profit. Either way antivirus OEMs have to keep full time staff that are constantly working against the clock. While some of these companies may have creative revenue models (e.g. Zone Alarm's Trial Pay), the bottom line is that their product will only be as good as the professional researchers that they can employ. Having said all that, AVG makes a good free product, but you have to manually update it yourself (daily).

2) Antispyware: like antivirus requires some updating and for the same reasons.

3) Firewalls: they need some updating from time-to-time. Hackers eventually find new ways of compromising security.