I can’t explain why, but SpeedFan may refuse to start automatically with Windows, whether it is placed on the Start menu startup folders or in the registry startup keys.

It seems that the only way to have it started with Windows is to create a task with the Scheduler.

Open the Windows Task Scheduler and create a new task with the option to start SpeedFan at your Logon, with the Highest Available Privileges, and after a delay of 15 minutes.

Enjoy!