Windows has its own firewall, but many studies show that it is very weak and vulnerable to a lot of exploits. So, if you do not have a good firewall installed on your PC, then it is as good as having no firewall at all. Here is how to test Firewall’s efficiency?
PC Tools Firewall Plus is a powerful free personal firewall for Windows that monitors applications connect to the network and stops Trojans, backdoors, keyloggers and other malware.
The program is not designed just for experts; everyone can use it, because powerful prevention against attacks and known exploits is activated by default. Experienced users can optionally create their own advanced packet filtering rules, including IPv6 support, to customize the network defenses.
The new version is designed for Windows 7 (32/64bit), Vista (32/64bit) and XP (32bit). Download from here.