Everybody should have an antivirus on their computer.  I recommend PC security Shield.  The antivirus is powered by F-secure antivirus and include realtime, scheduled, manual and heuristic scanning.  The Shield Deluxe suite is available now for $20 off making it only $19.99.  The Shield Deluxe also includes adware and spyware realtime protection.  I have used Norton for years, but I find it really slows the computer down.  Norton seem to utilize way to much CPU and conflicts with so many things.   Don’t even think about running Norton system works.  The reviews on PC Security Shield are pretty good with high marks for the Anitivirus and Antispyware capabilities.  It does appear to get some knocks for customer service, but I personally find calling any software company is terrible at best.  Get The Shield Deluxe at Half price at Savings Headquarter and pay only $19.99.