KASPERSKY WITH DAILY UPDATES DOWNLOAD IT AND UPDATE EVERYDAY...OR NOD32 And NOrton internet security 2009 which uses low system resources But all Antivirus needs a daily update for ur security...
1. KASPERSKY
2.NOD32
3. NORTON INTERNET SECURITY 2009

BIT DEFENDER HAS MANY FALSE THREATS.BELIEVE ME it ruins u r system if u r not professional