Antivirus or anti-virus software is used to prevent, detect, and remove malware, including but not limited to computer viruses, computer worm, Trojan horses, spyware and adware, dialer, key logger and rootkit infections. Earlier when i was using windows xp I always worried about viruses and i used to search for many free anti viruses during that period. In that searching period i used many free anti viruses for my PC. Now a days I didn't much care about antiviruses since i am using some premium antivirus for my pc.
Here are the best free antivirus programs for Windows. This list is based on how well they detect and protect system from malwares and viruses. Because of the increased number of virus attacks systems should be protected using antivirus. In that case this particular free antivirus review will help you to find best antivirus for your windows P C.
Avast Free Antivirus
Avast free antivirus is the first one that i am mentioning here. They recently released avast! Free Antivirus 6. Which is available for download from their site. This particular version is very use full for protecting your PC from malwares. But for further protection you can buy their pro antivirus or internet security. Your system requirements
©Avast
Operating Systems
Windows 7 (any Edition, 32-bit or 64-bit).Windows Vista (any Edition excl. Starter Edition, 32-bit or 64-bit). Windows XP Service Pack 2 or higher (any Edition, 32-bit or 64-bit). Microsoft Windows 2000 Professional Service Pack 4
Minimum Hardware Requirements
Pentium 3 Processor, 128 MB RAM, 200 MB of free hard disk space
Above given requirements are minimum requirements to run avast free antivirus to run on your PC. DOWNLOAD
Avira Free AntiVir Antivirus
Avira is my favorite among this list of free anti viruses. I think this antivirus was widely
Avira
used antivirus in the recent past and it is still going strong. It was very good when i was using it in the recent past. Now a days most of the people stopped using it because of best performances of other anti viruses. They are not mentioning more about system requirements or other details needed to run avira on a PC. Any way avira should work with most modern system properties. It will work with Windows xp/vista and Windows 7. You can download avira free antivirus.
Microsoft Security Essentials
An antivirus from Microsoft. It is a very good antivirus for popular versions of Windows Operating systems. I checked it with windows 7 and is working fine with my PC. You need a Genuine windows OS to use this particular antivirus. Still there are some draw backs for this particular free antivirus. One of the main disadvantage is its slow performance. But security essentials is available in many languages. So users from different countries can use this security essentials to give more protection for their PC. Download Microsoft Security Essentials.
Avg Free Antivirus
Avg Antivirus is one of the best antivirus for PC protection. I used avg for all most one year 
and will give a full rating for this particular antivirus. And it is a free version of antivirus and it will be free for all ways. There are many factors to give a very good rating for this particular product. This particular antivirus is very useful for home PC's because its easy to install and simple to use. Avg will not affect performance of your PC. Very good for personal data protection. Avg free will work with windows xp/vista and 7.
Avg Free Antivirus Download
Panda Cloud Antivirus
As it names suggests it is a cloud antivirus. This free cloud antivirus is best among the free 
anti viruses. They take free antivirus into a new level. Some of the strong reasons to recommend panda cloud antivirus: Real-time protection against all types of viruses. Automatic & transparent upgrades of new engine and program versions. URL and Web filtering of malicious, drive-by exploits and phishing sites. Product localized into 20 different languages.
Basic requirements are 64 Mb of ram. It will work all versions of windows like windows XP, Vista and Windows 7
Panda Cloud Free Antivirus Download
Comodo Internet Security
Comodo Internet security is one and only internet security which is available for free of cost. Can use it for business purposes as well.
System requirements:32 & 64-bit Windows 7 / Vista / XP SP2, 152 MB RAM, 400 MB hard disk space. Recently they released 2012 version of their Comodo Internet Security PRO. Download Comodo Free Antivirus
Malwarebytes
Malwarebytes is a small Free Antivirus which is very reliable to fight against malwares worms, trojans, rootkits, rogues, dialers, spyware etc. Main advantages of using this antivirus are It is a small antivirus and give more security. Powered with Advanced Malware Detection and Removal.
Malwarebytes Free Antivirus Download
Conclusion
There are plenty of free antivirus software's. Selecting the best one will help you to protect your PC from viruses. One of the valuable point is"Don't use more than one antivirus in a same OS". It will badly affect performance of PC and will give more bad results than good results.
erick
ramnadh