The problem is, its usually free for a limited period and once the trial period is up you are faced with the choice of buying a subscription or going unprotected. There are however, some free options available. A quick Google search will yield many free options.

Before considering any antivirus solution, you should check their itW (in-the-Wild) certification. ITW test are anti-virus tests done on malware and viruses that have been reported by multiple WildList reporters (typically Anti-Virus vendors) to the WildList Organization (WLO). A programs itW certification can be found by consulting any of the following organizations web sites: VB100%, ICSALabs, or Checkmark.

Three popular anti-virus programs are listed below. All three have good reviews from both users and independent reviewers.

AntiVir PersonalEdition Classic

AVAST 4 Home Edition

AVG Free Edition