When Messenger (Sign in thing) is opened, click the "mini blue question mark icon" on the right side of your picture avatar, then click show "menu bar".

The mouse over to the tools tab above and click "options", then click the "sign in" tab, then remove the check mark from "Automatically run messenger service when I log on to Windows".

Click "Apply" then "OK". When you restart next time Messenger will not open until you manually open it.

:)

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