According to toptenreviews.com,
BitDefender AntiVirus Pro 2011 is the most purchased Antivirus. BitDefender AntiVirus Pro 2011 have a complete features to proteck your computer.
Available features>>
Threat Detection: Virus, Worm, Trojan, Spyware, Malware, Rootkit
Additional Protection: Browser Exploits, OS Exploits, Keyloggers, Inbound Email Protection, Outbound Email Protection, Instant Messaging Protection, P2P/File Sharing Protection, Registry Startup Protection, Dialers, Backdoor, Hackers, Phishing, Identity Theft Protection, Adware, ActiveX, Vulnerabilities, Cookies, Scripts, Full Web Protection, Auto USB Detect
Protection Technology: Virus Signatures, Whitelisting, Heuristics, Real-Time.
Scanning Capabilities: On-access Scanning, On-demand Scanning, Manual Scanning, Quick & Deep Scan, Optimized Scanning, Scan Individual File(s), Exclude Files, Scan Compressed Files, Quarantines Infected Files, Auto-Clean Infected Files, Scan USB (and other external drives).
Additional Features: Password Protect Settings, Adjustable Security Levels, User Profiles, Self-Defense, Scheduling, History/Report Logging, Silent / Gamer Mode, Laptop / Battery Saving Mode, Link Scanner, Bootable Rescue CD, Free Virus Scan Online.
Updates: Automatic Definition Updates, Manual Definition Updates, Scheduled Updates, Pulse/Push Updates, Update with Proxy Server, Virus Defintions Updated (Hourly).
Certifications: Virus Bulletin VB100% Windows XP, Virus Bulletin VB100% Windows 7, ICSA Certified, AV Comparatives (A+), West Coast Labs Anti-Virus, West Coast Labs Anti-Spyware, West Coast Labs Anti-Trojan.
Technical Support: Phone Support, Email Support, Live Chat, Manual/FAQ/Knowledge Base, User Forum.
Supported Configurations: Windows 7 (32 bit), Windows 7 (64 bit), Windows Vista (32 bit), Windows Vista (64 bit), Windows XP (32 bit), Windows XP (64 bit),
unavailable features:
Spam Protection, Blacklisting & Security Network Protection Technology, Rollback and Scheduled Updated, West Coast Labs Anti-Malware Certification,
Recommended System requirements:
Operating system: Microsoft Windows XP SP3 (SP2 for x64), Vista (SP1), Microsoft Windows 7
Available free hard disk space: 1 GB free space
CPU: Intel CORE Duo (1.66 GHz) or equivalent processor
Memory (RAM):
1 GB (Microsoft Windows XP and Microsoft Windows 7)
1.5 GB (Microsoft Windows Vista)
Download Free 30 days trial on it's official site:
32bit: http://download.bitdefender.com/windows/desktop/antivirus/final/en/bitdefender_antivirus_2011_32b.exe
64bit: http://download.bitdefender.com/windows/desktop/antivirus/final/en/x64/bitdefender_antivirus_2011_64b.exe