John,
Create a new GPO (or modify existing):
Comp. Config\Windows Settings\Security Settings\System Services
Double-click 'Messenger' in right pane and set to DISABLED.
Apply GPO to appropriate OU. Hope this is what you were looking for. I
believe this might take 2 reboots on the user's machine. First reboot
stops the service and the second disables it.
Brian
