This is one of the tip to stop Windows Messenger from running in Outlook Express.
[Start] [Run] [Regedit]
Registry Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Outlook Express
Modify/Create the Value Name according to the Value Data listed below.
Data Type: REG_DWORD [Dword Value] // Value Name: Hide Messenger
Value Data: [2 = Messenger Will Not Load]
Exit Registry and Reboot