Messenger Service, often used for sending excessive popups with adverts, is not important for Windows, thus it can easily be stopped.
Go to Start – Settings – Control Panel - Administrative Tools – Services
Find the Messenger Service, select it, right-click on it. In the given menu choose Properties.
In the opened window click Stop, wait until the service stops.
To prevent the autorun of the service choose the Startup type – Manual. Click OK, the window will close. You are done with this now.
Please mind that the Messenger Service is NOT the same as Windows Messenger.
All operations should be performed under administrator account.