Windows Messenger is used by systems administrators to send messages to computers on their local networks (for example, a message that the network is going to be down at a certain time). However, the service can be used by hackers to pop up messages such as ads on your computer. If you don't operate in a computing environment where you need to receive Windows Messenger messages, you can disable the service. Here's how:
Click Start | Control Panel.
Click Performance and Maintenance.
Click Administrative Tools.
Double click Services.
Scroll down the list of services and highlight Messenger.
Right click it and select Properties.
Click STOP.
In the Startup Type, select Disable.
Click OK.
Note that Windows Messenger is not the same thing as MSN Instant Messenger. Disabling Windows Messenger will not affect your ability to send instant messages over the Internet.