Have you tried to open the Win task manager (CTRL+SHIFT+ESC keys), go to the third tab (1st applications, 2nd processes, 3rd tasks? - I'm using a german version of Win7, so I don't know the exact names), sort the tasks for their status (klick on the column header 'status') and take a look, which task starts 7 minutes after PC startup.
Maybe you can pin down the faulty task and can change it in a way that it does not influence P3D in the observed way.
Michael.