Microsoft Security Essentials is a new, free consumer anti-malware solution and spyware protection for your computer. It helps protect against viruses, spyware, and other malicious software. The tool offers free spyware protection, and it's available as a no-cost download for Windows XP SP2 and higher, Windows Vista, and Windows 7.
Visit
Here for more details and to download.
Download the latest definition updates for Microsoft Security Essentials manually by clicking the links below.
For Win x86 based pc visit
Here.
For Win x64 based pc visit
Here.
After downloading the file double click on it. MSE will be updated then. If you want to update it directly you can update it through the MSE itself by clicking on Update.