The Microsoft Baseline Security Analyzer (MBSA) is a free standalone vulnerability assessment tool that can scan your Windows systems to identify common security mis-configurations and missing security updates. The MBSA also includes a graphical and command line interface that can perform local or remote scans of Microsoft Windows systems.
MBSA 2.1 added support for Windows Vista and Windows Server 2008. MBSA 2.1 also provides full 64-bit installation, scan tool and vulnerability assessment (VA) checks, improved SQL Server 2005 checks, and support for the latest Windows Update Agent (WUA) and Microsoft Update technologies.
More information on the capabilities of MBSA 2.1 is available on the MBSA Web site.