On September, 28th 2009 Microsoft released Microsoft Security Essentials free for genuine copies of Microsoft Windows. Read more about the release the Microsoft Malware Protection Center team blog or read the official press release.
Qouting the team blog "Microsoft Security Essentials is a new, no-cost, anti-malware solution for genuine Windows PC consumers that provides real-time protection against viruses, spyware and other malicious threats. It is a lightweight, effective and modern anti-malware which runs on 32 bit and 64 bit Windows 7, Windows Vista and Windows XP SP2 and higher, and on modern consumer form-factors such as netbooks."
Visit the Microsoft Security Essentials Website to download your copy now..
For more free software and services check out the BlogMS resource guide to Microsoft Free Software and Online Software.