Microsoft Security Essentials can also be used by small businesses on up to 10 PCs!
Microsoft Security Essentials provides real-time protection for your home or small business PC that guards against viruses, spyware, and other malicious software.

Microsoft Security Essentials is a free* download from Microsoft that is simple to install, easy to use, and is automatically updated to protect your PC with the latest technology.

Microsoft Security Essentials runs quietly and efficiently in the background so that you are free to use your Windows-based PC the way you want—without interruptions or long computer wait times.

Before installing Microsoft Security Essentials, we recommend that you uninstall other antivirus software already running on your PC. Running more than one antivirus program at the same time can potentially cause conflicts that affect PC performance.

Download it Free -> Microsoft Security Essentials

The Myths of Security: What the Computer Security Industry Doesn’t Want You to Know

This book tells you:

Why anti-virus software doesn’t work well — and one simple way to fix it