If you are an average home user, there is no reason you should have to pay for your antivirus software.  If you are a business, or do a lot of web surfing, then I urge you to purchase good protection.  The following are some great options for FREE virus protection…

AVG Antivirus Free Edition 2012
Avast Free Antivirus 7
Avira Free Antivirus 2012
Microsoft Security Essentials 2.1

All four of these programs do a decent job of protecting your computer from nasties.  Just make sure you keep your security software updated and run regular scans.  Of course, nothing beats good old common sense – don’t open anything or click on any link that you are not sure of.