There you go!! Umpteen number of times I have mentioned on this blog how big a fan I am of NOD32! The reason being it is the simplest and the lightest Antivirus / Security Suite I have ever used. It is absolute no-nonsense antivirus software which does the job as good as any other AV (if not better) but mainly uses very minimal resources.
Raymond (yet again!!) has come out with a long but effective way to get free 6 months subscription of NOD32 AV. Check the link below for the detailed step-by-step explanation.
IMPORTANT Note: I would like to let you know that the process involves working with proxy. He does explain where to get the proxies from and how to use them though.
FREE ESET NOD32 Antivirus v2.7/3.0/4.0 Username and Password with 6 Months Subscription for EVERYONE