After trying most firewall Software I found "Sunbelt's VIPER the best. It's not free but you don't get ANY pop-ups eider. Plus it's not as resource hungry as most of the others. And if you combine it with the Viper security you won't even know it's running in the background. Absolute minimum resource usage less then any other Security software. Well worth a try.
Windows firewall is OK. It is not the best out there in terms of blocking according to several tests. But it is definitely adequate and it is not resource hungry.
The reason I don't use it is it is not easy to configure to control outgoing which is my primary requirement in a software firewall.
Before I was behind a hardware firewall, a guest downloaded a Trojan (using XP). ZA caught it as it tried to connect to the internet. I was able to clean it up promptly before it could do any damage. Since then, I want a software firewall that I can easily configure for outgoing. Windows firewall would not have caught that outgoing for me.
ZA is the easiest to configure of the free firewalls I have tried. Comodo is next followed by PCTools. PCTools had a better security rating than Comodo in two of the three tests I reviewed.
All that said, a properly configured hardware firewall offers the most security.
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