Download NeT Firewall
NeT Firewall is a really effective software that protects your computer from any intruder's attack.
It monitors and finds each packet, scans them and make sure they are not malicious or can damage your system. It prevents any kind of virus to stole any important information stored in your system. With each new version this firewall improves its security policies and database.
NeT Firewall is a free trial software of 30 days. It's not as powerful as other firewalls but is in the top of the list. You can try it out with many compatible Windows operating systems, from Windows XP to NT.