Non pas de lien  avec Marmiton c'est lié à des taches programmées (tu n 'as pas lancé autoruns ? parce que du fait que tu disais n'avoir que des tâches annexes je m'étais orienté sur autre chose)
 
 
Essaie cette méthode
 
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There are two scheduled tasks un Task Scheduler Library/Microsoft/Office:
 
OfficeBackgroundTaskHandlerLogon that runs when a user logs on
and
OfficeBackgroundTaskHandlerRegistration that runs every hour
 
Both were set to run under the "Users" account group. Since I didn't notice any popup at logon, I set OfficeBackgroundTaskHandlerRegistration to run under the "System" account and the hourly popups are now hidden. (Select the task, right click, Properties, click on 'Change User Or Group', type 'System', OK twice and voila.)
 
This is not the best solution from a security point of view, but until MS fixes it, it works for me.