Windows Live Sign-in Assistant is an Internet Explorer add-on that comes included with Windows Live Smart Clients, such as Windows Live Messenger. The goal of this add-on is to help make your sign-in experience faster and more convenient for users that have more than one Windows Live ID account.
Microsoft now released Windows Live ID Sign-in Assistant 6.5 beta that installs the Windows Live ID online provider for Windows 7. By making it possible to link a Windows Live ID to a Windows 7 user account, this online provider helps enable Windows 7 applications to deliver great features like sharing documents, pictures, music, and video.
More info: Download