Most, if not all of these free anti-virus software's are okay, but for full protection I would always recommend getting a comprehensive protection package which will have additional security over and above the anti-virus. Over the years I have used most of the free applications, and in all cases, I have had problems, for the last three years I have used Norton 360 All in One Security, it's been fantastic, warms me of possible problems. If you shop around you can get it for around £30, but you need to buy annually. At the end of the day, it will cost far more to have your infected computer sorted out, I speak from experience. You get what you pay for.