Greetings Newbie,

There are several differences between the two. Most notably, MSN Messenger 6 has support for
display pictures, custom emoticons, has a different interface, etc. whereas Windows Messenger
supports SIP-based communications services, Exchange IM Server, etc.  Which one you use is up
to you, and a matter of personal choice (and based upon your needs and likes), however one
thing to keep in mind, Windows Messenger must still be installed on Windows XP in order for
MSN Messenger to retain full functionality (Remote Assistance, Whiteboard, Application
Sharing, etc.).  You can just disable Windows Messenger by opening it up, click Tools,
Options, Preferences tab and unchecking 'Run this Program when Windows starts' or 'Run
Windows Messenger when Windows starts' (depending on version).  As well, you can disable it
further by going to Start, Control Panel, Add or Remove Programs, Add/Remove Windows
Components on the left, uncheck Windows Messenger in the components list and click Next >.
Note: this is only available if you've installed Windows XP Service Pack 1 -- if you haven't,
visit http://windowsupdate.microsoft.com.  This won't remove Windows Messenger, but it will
let it stay out of your way.

MSN Messenger is centered around MSN technologies (Hotmail, MSN Member Profiles, MSN Mobile,
etc.) whereas Windows Messenger is centered around Windows technologies (Exchange Server,
Office Live Communications Server, Windows Netmeeting, etc.).

Both clients however can make use of Microsoft technologies, like the .NET Messenger service,
.NET Passport and .NET Alerts.
____________________________________________
Jonathan Kay
Microsoft MVP - Windows Messenger/MSN Messenger
Associate Expert
http://www.microsoft.com/windowsxp/expertzone/
Messenger Resources - http://messenger.jonathankay.com