Which is the best antivirus software that has a boot-time scan and works on a 64 bit operating system?

Hello friend, I am a computer engineer and i have used many antivirus software in my laptop with windows 7 operating system(64-bit). There are many antivirus software available in Market such as Norton, Avast, AVG & Quick heal. At last I would like to prefer Quickheal anti-virus software which is accurate in boot scanning.

Quick Heal AntiVirus Pro protects your laptop and desktop PCs and provides protection against malicious threats that can slip into your system when you are surfing the Internet, check email, chat, etc. After the installation, which acts as a shield against viruses, worms, trojans, spyware and other malicious viruses. It also provides security against new and unknown threats with a technology called Quick Heal is DNAScan. It uses minimum system resources, thus giving complete protection to your system without reducing speed of system.

System Requirements : Platforms

1. Windows 2000 Professional
2. Windows XP (SP2) Home/Professional
3. Windows Vista Home Basic,Home Premium, Business, Enterprise, Ultimate (32-bit and 64-bit)
4. Windows 7 Starter, Home Basic, Home Premium, Professional, Enterprise, Ultimate (32-bit and 64-bit)