There isn’t one. Microsoft It will be replacing it with Skype.
March 2013 will be end for what started out as MSN Messenger in 1999. In it’s heyday, if you wanted to ‘talk’ to a friend across the world, it was the cheapest and clearest option around.
In the meantime, Windows Live Messenger does not co-exist well with Windows 8. I have managed to start it up just twice. All other attempts have left the machine hanging. So now it has been uninstalled and Qnext installed in it’s place. Qnext is a social connector which covers four exits.. see here..
Not surprisingly, I use the desktop version because I am old-fashioned and don’t like what I type being splattered over a wall for all to see.
Anyway, it’s free, it works, it has more than one use, and the PC Messenger version can handle other messenger services..