Avira AntiVirus Personal Version 10 available for Windows and UNIX/LINUX version.
Avira is one of the best antivirus software in the planet with high loading speed and not much use of memory on computer.

Zonealaram is the TOP most pc security (Anti-virus, Anti-spyware, FIREWAll) software in the world
5 reason for why you need Zone alaram :-

Norton release its beta 4.0 version of Norton-360 for the year 2010 & you can download the trial software absolutely free
Top 3 Reason for downloading the software :-

Trend Micro Internet Security safeguards your computer against Internet attacks(Hacking), cybercriminals without affecting your computer performance. This is a free antivirus software
Trend Micro comprises :-