Windows Defender Released (RTM)
Simply put Windows Defender is FREE anti-spyware from Microsoft. the official description reads as - "Windows Defender is a free program that helps you stay productive by protecting your computer against pop-ups, slow performance and security threats caused by spyware and other potentially unwanted software."
Defender has been in BETA for quite sometime. It has now been released as a supported product at:
With BETA phase, the product gained huge maturity with community support (SpyNet). It is one of those elements that are quintessential to any PC installation. So, if it is not still on your PC, get it on!