I would go back and check System Mechanic’s [B]settings[/B].
It sounds like it has been scheduled to “do something” at boot time. Perhaps a boot time defrag ?
Also, check your Startup Folder for any uninvited guests that may be trying to load at Startup.
I like WinPatrol for managing my Startup Folder.
Its primary function is Registry Watchdog if you choose to let it run in real time.