If you ask ten technicians what antivirus they would recommend for Windows, you will most likely get ten different answers. Opinions vary widely. One thing is for certain, there is no right answer to the question. It is an opinion, just like any other. If you are a home user or have less than 10 employees there are some free choices out there you may be interested in. Watch out for the word free–often they mean a trial. (I will not include trials here.)
There are several people that will tell you that the free antivirus programs are not as good as the paid versions. That is just another opinion and it is up to you to decide the answer to that question.
The best protection again viruses is education, know what to look for. Educate your employees on how to prevent infections from fakes, don’t download unknown software. If in doubt–ask. If you don’t have an education program in place, contact me.
One of the most popular free antivirus for Windows right now is Microsoft Security Essentials which you can get at www.microsoft.com/security_essentials. It is good (and free) for home users or small business clients up to 10 users. If you have more than 10 users, Microsoft wants you to look into their paid Frontline Endpoint Protection. But as far as free, Security Essentials is about as good as you can get for Windows. Their only requirement is your Windows must pass Validation.
Another free antivirus is ClamWin. ClamWin is open source software. Unlike most antivirus software, ClamWin does not have an Active Real-Time scanning engine. You must run it manually. I would not normally recommend this for your average, every day user. I would however recommend it for more advanced users or as a manual scan option. Combining Microsoft Security Essentials (MSE) and ClamWin can add to your protection. MSE has the active engine running. ClamWin can manually be ran on a time schedule.
AVG Free version is a fairly well known free version software. It is a scaled down version of their full product. The definitions are limited in the free version as are the features. It is meant to be a very basic antivirus with limited protection. If you plan to use AVG Free, I would recommend a second malware application as well to cover the limitations. You could use the free on-access scanning for AVG and a manual ClamWin scan on a schedule to better protect yourself.
My last suggestion would be Comodo Antivirus. I do not know much about Comodo other than they have a free version of their software available. It appears to be, in much that same what as AVG, a scaled-down version of their original. As with AVG I would suggest a secondary protection software as well.
Again, there are hundreds of antivirus products on the market promising to keep your computer safe. If you are going to use these products and spend sometimes hundreds of dollars to protect your computers, do your research. There may be free options out there that are just as useful. Often the investment in money that you save requires an investment in time. Since Time Is Money, you may want to weigh your options.