A lot of people are getting confused between all these "Messengers" that Microsoft have in Windows XP. The two in particular that people get mixed up between are Windows Messenger and Windows Messenger Service
Windows Messenger- An instant messaging program bundled with Windows XP which is not as secure as MSN Messenger and starts when you start Outlook Express. The same concept as MSN Messenger but not as good. You can download it from Microsoft. It is also used to get Remote Assistance.
MSN Messenger- A brilliant and popular Instant Messaging program that lots of people use available for download from MSN. Much better than Windows Messenger.
Messenger Service- An annoying feature in Windows 2000 and XP that was originally designed for Network Administrators to send messages to users across their Network. Some people have taken advantage of these feature and used it to send advertisements to people connected to the internet. For more information about Messenger Service and some websites that actually offer this software to Spam people visit Grc- Shoot The Messenger. You can also download a small 22KB application that lets you Disable/Enable Messenger Service without any hassle.
Owen, http://www.isecurity.org.uk