Over the years, Microsoft has been through many name changes with its services. From MSN to .NET. to Windows Live, people for a long time just wanted one name that unified all of the services, making it much easier to remember.
Well it is coming. Windows Live is dropping its name, and now everything will become a "Microsoft Account".
In his latest blog post for the Building Windows 8 blog, Microsoft's Steven Sinofksy explains the company's new approach to cloud services in Windows 8 and Windows Phone, and confirms one big change: it's doing away with the Windows Live brand entirely. Replacing it is something simply called the Microsoft account, which you can use to both sign in to Microsoft's own services and tie to other third-party services like Twitter or Facebook.
That one account can be used to sign into any of Microsoft's services and devices. In addition to the former Windows Live branded services, that includes the longstanding MSN Messenger, which will now simply be known as "Messaging."
For the full information, refer to the source below.
Source: Building Windows 8