A security issue has been identified that could allow an unauthenticated remote attacker to compromise your system and gain control over it. You can help protect your system by installing this update from Microsoft. After you install this update, you may have to restart your system. This update is provided to you and licensed under the Windows 7 Prerelease License Terms.
Learn more here
Download for Windows 7 32-bit here
Download for Windows 7 64-bit here
This security update also applies to previous releases of Windows including: Windows 2000, XP, Vista, Server 2003, and Server 2008. Learn more here