avast

avast! Free Antivirus represents the best free antivirus protection currently available on the market. This edition is FREE OF CHARGE for non-commercial & home use. Its features include:

• Anti-spyware built-in
• Web Shield
• Anti-rootkit built-in
• Automatic updates
• Strong self-protection
• Virus Chest
• Antivirus kernel
• System integration
• Simple User Interface
• Integrated Virus Cleaner
• Resident protection
• Support for 64-bit Windows
• P2P and IM Shields
• Internationalization
• Network Shield

Requirements : Windows 2000 / XP / Vista / Windows7 / XP64 / Vista64 / Windows7 64 / Windows8 / Windows8 64

Link : http://www.avast.com/index