I use the free version of Zonealarm. It works great on my PC and no complaints. But -and this is a big but- since they refuse to fix a security issue in the free version (as described in the thread Gankaku mentioned) I am on the lookout for a new free firewall, so I will be following this thread closely in hopes to find another simple but good firewall.
I found Avant browser because of this forum so I am sure somebody will come up with a good alternative
Hanneke