Windows Messenger is a proprietary instant messaging client included in Microsoft's Windows XP operating system. It is also available for Windows 2000 and Windows Server 2003, beginning with version 5, but is not included in Windows Vista.
Windows Messenger should not be confused with the similarly-named Windows Live Messenger (formerly known as MSN Messenger), which is a separate instant messaging product available for download from Microsoft. It is also not related to the Messenger Service, which is a component of Windows NT's LAN Manager.
Windows Messenger has been superseded by Office Communicator in corporate environments and Windows Live Messenger for .NET Messenger Service connections.
