free antivirus

Having an anti-virus package should be an essential part of every computer, although many home users still go without. The good news is that there are several excellent free anti-virus applications available, so there's no excuse not to install one.
Ineffective anti-virus software is almost as bad as having no protection at all, so it is strongly recommended that you go for reputable and well-supported package. You can check the performance and detection rates for many of the big players at http://www.av-comparatives.org/, an independent anti-virus testing site. Using this site you can make sure that whichever package you choose consistently ranks well in tests.
Rather than listing all the free anti-virus solutions, this article will provide links to software we can vouch for. Not all products are created equally, and our current recommendation would be Avira, closely followed by Avast.
Avira AntiVir:
URL : http://www.free-av.com/
Avira is highly recommended by many of our forum regulars and consistently ranks well in AV-Comparatives.org testing. If you are looking for a great, free AV solution then this would be our current recommendation.
Avast:
URL : http://www.avast.com/
Avast puts in another good performance in the anti-virus tests, with especially good scanning times. This is a good all-rounder and a sound alternative to Avira.
AVG:
URL : http://free.avg.com/
AVG is a popular choice for a free anti-virus solution, however the test results aren't as high as the previous two recommendations. Although easy to use, the detection rates and scan speed let this software down.
Microsoft Security Essentials :
URL : http://www.microsoft.com/Security_Essentials/
MSE is a relative newcomer to the anti-virus pack, so it may be worth waiting to see how it performs before relying on this software for your system security. Current AV tests only include the results from the previous incarnation of this software (called OneCare) which may have been improved upon.