http://www.personalfirewall.comodo.com/
http://www.personalfirewall.comodo.com/download/setup.exe

It's Free. Forever. No Catch. No Kidding
WHY FREE?
What's for free?
Comodo is delivering this highly rated firewall free as a cornerstone of our initiative to empower consumers to create a safe and trusted online experience whenever you go online. This new initiative will also make available other free desktop security tools to avoid leading threats such as phishing attacks. The free tools include: the ability to authenticate web identities in real time (www.vengine.com), free email certificates for secure email encryption, secure backup for backing up files on your pc and iVault for password management and launching secured internet sessions. Together, all these solution could cost upwards of $500 per year to achieve a comparable level of internet security and safety. And all these products are offered free for the lifetime of the PC - without any annual subscription fees or licenses.

Why is it free?
You must be wondering - how can we stay in business by giving away high quality solutions that all other software vendors sell. Simply, Comodo's main revenue comes from authenticating web business with SSL certificates (e.g. we put the padlock on websites). The more consumers are comfortable being online and shopping online, the more businesses that will be created that will need our services.

It's the ultimate win/ win.

Consumers get business class desktop security solutions for free, emerchants get a new, growing pool of confident online customers and Comodo gets to sell our technologies and services to all these eMerchants.

And this is our CEO's explanation as to why its free!
http://forums.comodo.com/index.php/topic,764.0.html