Windows Live Messenger 9.0 Build M1 in All Its Splendor- The dogfood version is part of Windows Live Wave 3
Microsoft is making headway with the development of Windows Live Wave 3, designed to provide major updates to the second wave of services and 
solutions collectively released under the Windows Live brand umbrella at the end of 2007. In this context, the Redmond giant is also cooking an upgrade to Windows Live Messenger 8.5 made available in early November of the past year. The first Beta of Windows Live Messenger 9.0 went live and was leaked in November 2007, with Microsoft pulling the plug on the testing phase as of June 24, 2008. But now the software company has moved forward in the development process to the 2009 version of the instant messaging client, namely Windows Live Messenger 9.0 Milestone 1.
According to Mess.be and LiveSide, which jointly provided the first details related to Windows Live Messenger 9.0 M1, the build, also leaked, but not yet available for download, is the Windows Live Wave 3 Milestone 1 installer of the next generation Microsoft IM client. Windows Live Messenger 9.0 M1 is the successor of the initial Beta dropped at the end of the past year, but continues to be labeled as a beta release itself. Version 2009 of Messenger 9.0 is Build 14.0.3921.717, and very much still a Beta release, with the software company laboring to produce Milestone builds while making its way to the official launch reportedly planned for the end of 2008.
For more details: Softpedia