AVG Anti-Virus Free Edition. Its easy to use and will not slow your system down and it's does not eat up all the computer resources.Functionality based, AVG is the best. they're easy to use and very suitable for all people.
I am using Avast 4 home edition. It is free antivirus software. It is designed exclusively for non-commercial and home use only.It is possible to avoid global virus spreading by efficient prevention.
I am using Kaspersky Anti-Virus. It offers maximum spyware protection to guard against viruses, Trojans, and worms, spyware and adware, rootkits, identity theft and phishing attacks.