Comodo Internet Security is a free, very voluminous and multi-layered security application that keeps hackers out and personal information in.
If you prefer a smaller solution with Antivirus Protection only: see http://alternativeto.net/desktop/comodo-antivirus.
Built from the ground upwards with your security in mind, CIS offers 360° protection by combining powerful Antivirus protection, an enterprise class packet filtering firewall, and an advanced host intrusion prevention system called Defense+.
CIS Includes:
Firewall: Slam the door shut on hackers and identity thieves.
Antivirus: Track down and destroy any existing malware hiding in a PC.
Defense+: Protects critical system files and blocks malware before it installs.
Memory Firewall: Cutting-edge protection against sophisticated buffer overflow attacks.
Anti-Malware Kills malicious processes before they can do harm.