Which one is the best free windows antivirus software?

I’m looking for the best free windows antivirus software, Can you help me? Please give me the reason why is the best and the link to download it?

Thank you,
Salvador Hernandez
Who is Participating?
For me it is definitely Panda Free Antivirus. It is very light on system resources as most of it's work is done "in the cloud". I've used it for years and never had an issue (I used Avast! free and sometimes Avira free earlier, but those used a lot of system resources, and often caused crashes).

But of course, as with most free AV solutions, you are only allowed to use the free version if it's for private use. If you use it for business, then the only option is to use M$'s security essentials, which you can use on up to 10 PC's in a business (including servers before 2012 server, other free AV products don't run on server OS's).

Are you looking it for personal or business use?
For business use the selection is really limited:

If you are asking about AV for home use, I would probably install avira.
But I can not say it is the best free AV. You are anyway selecting from a bunch of limited AV solutions (and annoying ads).
Natty GregIn Theory (IT)Commented:
Comodo antivirus all the way, sophos and clamav
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David Johnson, CD, MVPOwnerCommented:
There is no 'BEST' Panda and AVG rated the highest as per PC Magazine
The problem most users have is Unwanted Software that was installed as a tag-along when installing free software and only user education and the user paying strict attention when installing any software
Dr. KlahnPrincipal Software EngineerCommented:
I find AVG suited to my taste.  If you pick a highly rated antivirus, they all do detection well and it comes down to "I like the way this one looks" or "I like this interface better."

I agree 100% that unwanted software is a problem.  It is tiresome to scrutinize every check box and description to find out if one of those "that looks right" options actually installs unwanted commercial bloatware.
shamigc3 --
You asked for "free".
There is no one antivirus app that is best.  Each has it strong points.  The purveyors of malware are very aggressive.
I use Microsoft Security Essentials as antivirus.  

And scan perhaps once a week with free MalwareBytes.

No problems for five years.  But I also practice "safe surfing" and try hard to not access sites that carry malware.
Dave BaldwinFixer of ProblemsCommented:
I use Avast.  But I always do a custom install to avoid all the 'features' they want to give me.  There are two of them that can turn your computer, especially an older one, into a slug.  One is the Updates scanner that constantly suggested updates that can't be installed on my computer.  Don't remember what the other was.
shamigc3Author Commented:
I want it for personal use.
At our office we use ESET NOD32, its a great software,  you could also check others
i use also panda cloud free now - and find it very good, also for the reasons Rindi gave
EirmanChief Operations ManagerCommented:
Once you have chosen an anti-virus program you should consider extra protection against
CryptoLocker type malware. This type of RansomWare is becoming very prevalent and is
causing much grief out there.

The free version should suit for most purposes.
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