Microsoft has once again confused things. There are TWO Windows Messengers PLUS MSN Messenger. ONE of the Windows Messengers (Which I believe is only is XP) IS a chat service but does not have as many options as MSN Messenger does, the other is an Admin Service like you are saying Ray. Lavasoft (The Ad-Aware) people have plug-ins available for Ad-Aware SE that will block BOTH of the Windows Messengers from enabling (sometimes disabling them in the regular options from Microsoft does not work) BUT they are two seperate plug-ins. These two paragraphs (bold) are just the beginning of how Lavasoft describes the Admin one. Which they call. "Messenger Control"
"Beginning with Windows NT, Microsoft included the Windows Messenger Service, and it's been built-in to each subsequent version and release of Windows over the past several years. It was originally designed to allow system administrators on client-server networks to send out brief system-wide messages to everyone connected to the network. For the most part, it's never gained much use since there are easier alternatives to sending such messages.
It is being put to use however, by those who know that this Service is turned on by default in all current versions of Windows. If you've been connected to the Internet and suddenly see a window pop-up filled with information about the latest "get-rich-scheme," a college diploma, or low-rate credit cards, you're being spammed courtesy of Windows Messenger Service! Note that these are not browser windows, but resemble Windows Dialog boxes (with "Messenger Service" in the title bar), with the exception that you're generally offered no "options" besides clicking an "OK" button."
This is what Lavasoft says (bold) about the other one Windows Messenger which IS an instant messenger service which is supposed to open when Outloot Express opens ONLY on XP but it does NOT always work that way. Lavasoft calls that one "OE/W Messenger".
"Disable Windows Messenger From Appearing When You Open Outlook Express
Many users opt not to use Microsoft Windows Messenger for their instant messenger program. Despite the fact that Microsoft Windows XP users have turned off the auto-start feature of Windows Messenger, it continues to open when Microsoft Outlook Express is use.
It should be noted that this only occurs on systems running Microsoft Windows XP. Other versions of Microsoft Windows do not experience this.
If you have disabled Windows Messenger's auto-start function, and you'd like it to remain closed while using Outlook Express, we have created an add-on which will allow you to prevent Windows Messenger from starting when Outlook Express launches. The add-on allows you to switch between disabling and enabling Windows Messenger's auto-launch status when opening Outlook Express. When Windows Messenger is disabled, you may also notice faster load times when opening Outlook Express."
Hopefully that will explain things for you OR confuse everybody more than they already were. LOL.
As far as answering your question about which of the INSTANT messenger services are better, between the two Microsoft ones LuckyLady, MSN Messenger is better but there are also many other alternatives to both, such as ICQ, AIM, Yahoo Messenger, Trillion just to mention a few. I hope this has helped in some small way.