Zone alarm is free, easy to use, and causes very little problems if set up correctly. Have had it for years without any problems.
Most of the probllems are because the firewall is doing its job properly and blocking access to from PCs and people are trying to network etc, without telling the Zonealarm prog to allow access.
As free therefore no tech support from Zonelabs so people come here for advice.
ZA is better than most firewalls you have to pay for.
You cannot afford to be without a firewall, antivirus software and spyware blockers in todays sad world of computing.