Microsoft has finally retired Windows Messenger (Live Messenger, MSN Messenger) and is asking users (former users) to migrate to it’s Skype platform. Luckily, your contacts come with you with the transition.
I did prefer the simple Messenger over the more feature rich but beefy Skype. Skype is a great product, but sometimes I like the skinny client that doesn’t use much screen space or system resources (I’m OCD when it comes to that!).
Messenger was retired in April 2013 and is no longer available or supported on most Mac and Windows operating systems. *
You can continue to make audio and video calls with your contacts on Skype and Facebook and send IMs for free—your contacts will come with you when you update to Skype and sign in with your Microsoft account.