Windows Messenger vs Windows Live (MSN Messenger) Messenger
While Windows Messenger and MSN Messenger look very similar, they are, in fact, two separate applications. The good news is that either can be used to access the same .NET Messaging Service contacts. That's the default instant messaging service for both, and the one you'll use on the internet. What that really means is that if all you're doing is instant messaging your friends and family on the internet, it doesn't matter which one you use, and changing from one to the other is not a problem.
They are two different programs, have slightly different feature sets, and release on different schedules. In particular, Windows Messenger is more tightly integrated with various Microsoft applications. It is included with Windows XP but is also available with Windows 2000 and Windows Server 2003. Windows Live Messenger is available through a separate free download from Microsoft.
The differences, and the confusion, don't end there, though. There is yet another Windows "Messenger". On Windows 2000 and Windows XP there is a service, called "Messenger", often referred to as the "Windows Messenger", that is used to present what can best be called "network messages" to a machine's user. This is not an instant messaging application, but rather software that runs in the background, listening for incoming messages, and popping up a very simple box containing the message when one arrives. The most common example might be in a corporate environment when you send a document to a network printer. The messenger service handles the pop-up message that the printer sends back when it has finished.
Unfortunately the Messenger Service has been exploited by spammers to pop-up unwanted advertising messages on unprotected machines on the internet. The average user has absolutely no need for the Windows Messenger Service, and thus it can safely be turned off. To do so, go to Start -> Programs -> Accessories -> Administrative Tools -> Computer Management -> Services & Applications -> Services. Double click "Messenger", and set the "Startup Type" to Disabled. You can also "Stop" the service at that same dialog.
Finally, there's one more instant messaging client to briefly mention. If you play certain games on MSN's Gaming Zone, you may also be presented with a small application called "ZoneFriends". It's yet another instant messaging application,specifically forchatting among the folks you're playing your on-line games with.
