Hi Winston!
If you've set your Mac to automatically log in to your computer account and then set Messenger to automatically log in at login, yes, whoever has access to your Mac will see everything.
Your message history is stored locally on your computer. If you've chosen to automatically save all message conversations without asking then everything is there to see. But since your history is stored locally on your computer (not on the Live servers) no one else will be able to see your messages.
This group in Microsoft's forums is dedicated to Messenger for Mac, which is a Microsoft product and not an Apple product. <http://groups.google.com/group/microsoft.public.mac.messenger> You'll probably get more informative responses there rather than this one, which is dedicated to Mac and Windows compatibility issues.
Hope this helps! bill
1 GHz Powerbook G4 Mac OS X (10.4.8)
