5 best free Anti virus.

For those who want to use Anti Virus free of cost.
AVG
Anti virus and anti spy ware.
High detection rate.
Real time guard.
Schedule update.
Schedule scanning.
On demand scanning.

AVAST Home
Anti virus and anti spy ware.
Real time protection
Fast scanning
Boot time scanning
Schedule update
Schedule scanning
On demand scanning

AVIRA Anti vir.
AntiVir protection against viruses, worms and Trojans.
AntiDialer protection against expensive dialers.
AntiRootkit protection against hidden rootkits.
AntiPhishing protection against phishing.

Comodo
Detects, blocks and eliminates viruses from desktops and networks
Constantly protects with real-time On Access scanning
Built in scheduler allows you to run scans at a time that suits you
Daily, automatic updates of virus definitions
Simple to use: install and forget while CIS protects you in the background.

Bit Defenfer.
Anti virus and anti spy ware.
Real time protection
Auto update.