Microsoft announced that it is retiring Windows Live Messenger — its instant messaging client that works with many of Microsoft’s platforms — in favor of Skype.
The company plans to end Messenger in all countries worldwide in the first quarter of 2013 (except for in mainland China).
According to the official Skype blog:
This effort started with the release of Skype 6.0 for Mac and Windows a few weeks ago, which allows you to sign into Skype using a Microsoft account. Now Messenger users just need to update to the latest version of Skype, sign in using a Microsoft account, and their Messenger contacts will be there.