Anti-Virus
First of all, every PC should have rock solid anti-virus protection. There is so much "malware" out there on the Internet that no one can afford to be without one. Whether you use a free antivirus program or a paid one, you should most definitely have an anti-virus program, keep it up to date religiously, and run a full scan on a regular schedule.
There are pros and cons for free or paid antivirus products, and there are very good programs of both persuasions available, so the choice is yours. I will make some general observations here, and provide you options.
Over the years, I have used many free and paid anti-virus products, but I found some shortcomings with all of them that kept me looking for something better.
The paid products worked well enough most of the time, but required so many computer resources to run that my computer seemed to be crawling along. The definitions weren't always updated, and didn't always let me know when they were out of date so I could start an update. Plus, they got pretty expensive, and i still got infected periodically.
With most of the free antivirus products, their big shortcoming was that I had to continuously check to see if the definitions were up to date, and also make sure they were scanning my computer thoroughly when they did their scheduled scans. Many of them require you to run the scans manually. And to be honest, the protection let me down often enough that I lost confidence in their ability to really keep my pc safe.
Occasionally my computer would become infected by some malware that got through the free and paid program's vaunted layers of protection. I would have to track down and run the removal program for the "malware of the week," and became concerned that I was not getting the protection I wanted, even considering it might be free.
Searching for something better, I managed to find one that just worked, did its updates when it should (or at least warn me when it couldn't), and protect me and my family from all the bad stuff that was out there. So the program I chose was VIPRE I think it is one of the very best antivirus programs on the market. It is fast, efficient, reliable, very thorough, and most of all, it doesn't slow my PC down except when running a deep scan. I have yet to have an infection take over my PC completely since running this program (well, once, but it only took over until I rebooted my PC and ran a scan.)
This program impressed me so much that I purchased it for myself and all the computers I use in my home and business, and those of my wife and children. I also recommend it to all my clients, especially when their anti-virus product (either paid or free) has let them down and cost them a princely sum for me to repair.
Disclaimer: I am one of their affiliates, and if you buy from this link I will be compensated by them. (I do NOT think you need to buy the CD, you can always download the software from the web.)
Now I don't expect 100% protection, because no program can promise that in reality. If you are looking at one that claims that it does, back away slowly.
The day that a new malware program is released is called the "Zero-Day" and everyone on the Internet is vulnerable in some way from that "Zero-Day" attack, until their anti-virus or anti-malware software is updated.
When a new malware program is released into the wild of the Internet, none of the programs know what it looks like or how to cure it. That may not happen for some time, normally a day or two, as the anti-virus and anti-malware vendors are always trolling the Internet for new threats.
When they encounter malware they have not seen before, they immediately begin working on figuring out how to cure it, and when they do, they update their products immediately, and their clients are then protected.
VIPRE (and other programs as well, to be honest) has a heuristic anti-virus engine that looks at the behavior of any software that runs and not just the actual code. This makes it much more efficient at detecting bad behaviors and stopping them before they can do any serious harm.
With VIPRE, there is phone, chat and email support 24/7, and in the few instances when I have had to deal with them, they have been excellent. They are U.S. based, and very competent. Many free anti-virus products do not provide any technical support. That's not important -- until you need it.
if I were an individual, I would consider a free anti-virus program, but not if I were running a business. The small investment is worth every penny when your livelihood is at risk!
Important Note !! - Do not run more than one anti-virus product at the same time. They can seriously interfere with each other and can cause your PC to slow to a virtual crawl!
With that being said, I feel that if you still don't want to purchase an antivirus product, here are some worth looking at:
Avira Free anti virus (be careful not to install the ASK toolbar!)
AVG free anti virus (rated the best free anti-virus)
Microsoft Security Essentials (not the best of the lot)
Good luck and safe computing no matter which product you choose!