AVG seems to be a top competitor. We have one windows system and one apple system at each desk. In my personal opinion, just go apple. It's expensive but in the long run you don't have to worry about viruses or spending the money for an anti virus system.
Many options are available in the market like Avast,Guardian,Quickheal ,Norton etc. Microsoft security essential is the best according to me .
Microsoft Security Essentials pre-release is best in the cetegory. Or use Malwarebytes anti malware or Advanced System care pro with anti virus
According to my personal experience AVAST is really very best antivirus i ever found Try this once and you will enjoy awesome feelings
Avast is love, Avast is life. I've never met a Virus since I used this amazing tool over 7 years ago. Use it, and I'm sure you will not regret!
I personally use a combination of Avira and Malwarebytes, as both of them offer the "Antivirus" part of the program for free and charge for other perks. I don't quite understand why they'd offer the main program for free and sell you bells and whistles, but they do, so I use them. Also, I'd recommend using Noscript or Safescript and an adblock, as those protect you from a lot of viruses without being "traditional" antivirus.
I'm using Avast (silent and game modes on) in combination with free Comodo firewall. From time to time I'm using a free DrWeb tool - CureIt. Still in doubts what paid tool to choose - Kaspersky or DrWeb... they're both very powerful and are on the top.
I tend to use a combo of Avira (free) and Webroot (paid - but 5 licence subs are dirt cheap on ebay) on my machines. The exception is my main laptop as I've a Malwarebytes lifetime licence, so I combine Webroot with that.