i find that AVG is a very good anti-virus program, McAfee anti-virus is also very good. ive tried Norton but couldnt really get on with it. All can be downloaded from any share site, emule, bearshare, Kazaa etc. Another very good site to visit is
it offers all sorts of free programs, anti-virus, firewalls, anti spyware. you will find AVG anti-virus on that site. Spybot search & destroy is also available there, which i highly recommend. hope this helps.