Microsoft Security Essentials Prerelease 4.1

The Microsoft Security Essentials Prerelease program allows users to run the latest & greatest versions of Security Essentials before they are publicy available.
As a Microsoft Security Essentials Prerelease user, you will have the opportunity to explore and test new builds of Microsoft Security Essentials before they are publically available and provide feedback to Microsoft. Your feedback helps Microsoft to make its software and services the best that they can be. As a Microsoft Security Essentials Prerelease user, Microsoft Security Essentials updates will automatically be installed on your computer through Microsoft Updates. To help us improve the software, you will be enrolled in the Microsoft Error Reporting, Customer Experience Improvement Program, and Microsoft Active Protection Service.