Hello Andre,

As per you and Zeo, here is a possible timeline:

 1/2005
 2/2005
 3/2005 - XP 64 / Longhorn Alpha : Milestone 9
 4/2005
 5/2005 - Yukon / Visual Studio 2005
 6/2005 - Longhorn Beta 1
 7/2005
 8/2005
 9/2005 - PDC 2005 / Longhorn Beta 1.1
10/2005
11/2005
12/2005

 1/2006 - Longhorn Beta 2
 2/2006
 3/2006
 4/2006 - Longhorn RC1
 5/2006
 6/2006 - Windows Mobile 2006
 7/2006 - Longhorn RC2
 8/2006
 9/2006
10/2006 - Longhorn RTM
11/2006 - Longhorn GA
12/2006 - XBox2