Suppress OneNote adding itself to startup items
In OneNote 2010, from the Options menu on the Backstage file tab choose the Display option in the left menu and uncheck 'Place OneNote icon in the notification area of the task bar'.
In OneNote 2007, it is in the "Other" option, not the Display option.
I did all recommendations and it still opened. The duplication mentioned above made me think so I look at Norton manager for start ups and found one note in there checked on. So uncheck in there too and it looks like that did the trick.