I don't know if this will help you or whether it will still start up:
1. On the Start menu, click Control Panel, click Performance and Maintenance, and then click Administrative Tools.
2. Double-click Services.
3. Scroll through the list of services until you see Messenger, and then double-click it.
4. In the Startup Type list, click Disabled.
5. Under Service Status, click Stop, and then click OK.