Windows Defender No Longer Beta
Windows Defender is a free program that helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software. It features Real-Time Protection, a monitoring system that recommends actions against spyware when it’s detected and minimizes interruptions and helps you stay productive. Now with 2 free support incidents for Windows XP and Windows Server 2003.
Download: Microsoft Windows Defender (Free)
View: Windows Defender Homepage