Easily Disable Messenger

Go into: C:/Program Files/Messenger. Rename the Messenger folder to "MessengerOFF".
This does not slow down Outlook Express or hinder system performance.

i had to boot in to safe mode to do this(press f8 at boot screen)

I found this in a few different places around the 'net - hopefully it's helpful:

Easily Disable Messenger

Go into: C:/Program Files/Messenger. Rename the Messenger folder to "MessengerOFF".
This does not slow down Outlook Express or hinder system performance.

I totally got rid of Windows Messenger on our XP upstairs......

I closed it from the taskbar and then "ENDED TASK" on msmsgs.dll (Messenger DLL) .. I then deleted the MESSENGER folder. Then i went into the reg and deleted the keys for MESSENGER (I made sure it was the right messenger keys)