At last the long awaited replacement for the discontinued Windows OneCare suite.
Microsoft Security Essentials is Microsoft’s free anti-virus and anti-spyware solution. It is aimed at home users and small businesses and will be available for Genuine Windows XP, Vista and Windows 7 users and will be available in 32bit and 64bit editions for Vista and 7.
Below are the download links.
Windows XP Windows Vista/7 32bit Windows Vista/7 64bit