Quote Originally Posted by Microsoft
We will retire Messenger in all countries worldwide in the first quarter of 2013 (with the exception of mainland China where Messenger will continue to be available).
Full article here.

As most of you already know Microsoft bought Skype for $8.5 billion in 2011 and now owns two instant messaging services. It only makes sense, that the software giant wants to get rid of one of them and now this time has come. In the first quarter of 2013, Windows Live Messenger (and all clients using the Microsoft Messenger service) will stop working in almost all countries around the world, putting an end to a service, that's been around since Windows 3.1.

To allow users to still use the old Messenger contacts, Microsoft has integrated the Messenger service into Skype, but before this can start working, you will have to link the two accounts together. To learn how, read the full article above.

NOTE: Sometimes Skype says it's up to date even when a new version is available. In case this happens to you, check your Skype's version and make sure it's at least 6.0. If it's not, download Skype from their website, run the setup and the installer will update your old installation.