There are numerous Antivirus softwares in the market. I have seen people buying the expensive one thinking it will do the best job, but its untrue. I came across antivirus from Norton, McAfee are the common ones used, but same time they take up so much resource that it slows down your pc. I have been managing networks of 120pcs daily. From last 2 years I have been using Free Antivirus on 20-40pcs in my network and the result is superb, and its free of cost.

Try these free antivirus and forget about paying some to Norton or McAfee.

Avast! 4 Home Edition
http://files.avast.com/iavs4pro/setupeng.exe

Avira AntiVir Personal
http://www.free-av.com/en/trialpay_d...antivirus.html

AVG Anti-Virus Free Edition
http://free.avg.com/download?prd=afe

Trend Micro's FREE online virus scanner
http://housecall.trendmicro.com/

Comodo Firewall and AntiVirus
http://personalfirewall.comodo.com/d..._firewall.html

Ad-Aware (free Anti-Spyware)
http://lavasoft.com/single/trialpay.php

SUPERAntiSpyware (free Anti-Spyware)
http://www.superantispyware.com/down...NTISPYWAREFREE

my personal recommendation is AVAST or AVIRA.