Greetings Kevin,

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.).

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.

Which one you use is a matter of personal choice, based upon what functionality you need and
how you want Messenger to look.

To disable Windows Messenger, open it up (click Start, then Run, type "msmsgs" and click OK),
click Tools, Options, Preferences tab and uncheck 'Run this Program when Windows starts' or
'Run Windows Messenger when Windows starts' (depending on version) as well as 'Allow this
program to run in the background' or 'Allow Windows Messenger to run in the background'
(depending on version).
____________________________________________
Jonathan Kay
Microsoft MVP - Windows Messenger/MSN Messenger
Associate Expert
http://www.microsoft.com/windowsxp/expertzone/
Messenger Resources - http://messenger.jonathankay.com