EMET, short for Enhanced Mitigation Evaluation Toolkit, allows developers and administrators to add specific security protections to applications. Unlike mitigations released in the past, EMET doesn't require programs to be recompiled, so it can be used to fortify applications even when the source code isn't available.

http://blogs.technet.com/srd/archive/2009/10/27/announcing-the-release-of-the-enhanced-mitigation-evaluation-toolkit.aspx

-Urs