This is a copy paste from another help forum I'm on.
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If you are interested, the Microsoft Security Essentials Pre-release program allows users to run the latest versions of Security Essentials before they are publicly available.
Explore and test new builds of Microsoft Security Essentials before they are publicly available and provide feedback to Microsoft!
If you wish to be able to submit feedback to Microsoft about this program you have to register to the Security Essentials Prerelease program on Microsoft Connect.
Details and download here:
http://www.microsoft.com/en-us/download ... x?id=29942