To make my PC's performance faster, I relied on secondary scanners only. Now I use avast! though, since it is very lightweight. The best imo is Avira, with an extremely high detecion rate, but it is quite heavy.
I like Microsoft security Essentials. I have tried many others but this one actually cleaned up a virus on my computer so I trust it more than some others. I am sure there are many good ones. it is a matter of choice and service received
I am using BitDefender Internet Security 2011. It is a decent anti-virus and was rated as the top 2011 antivirus and I have not had problems with it so far.
I think this will be funny but I don't use any antivirus software. They use alot of memory and cpu for nothing.Once a month, I use malware bytes to check for malwares on my pc and that's all. I know what I download from the internet and I kannot be infected.
I use Microsoft Security Essentials. Before this i have used a lot of antivirus programs, but never have been happy. Microsoft Security Essentials is very easy to use, and moreover does not affect your computer speed. It is also very powerful in identifying viruses.