You will find HDD Fan Control in your downloads folder.
It's both the demo and the full version (with license):
You can try it out for 1 hour after installation
then you must purchase a license to unlock the full version.
Instructions and Help for HDD Fan Control can be found in Support.
Reduce Fan Noise and Protect your Drive.
We have launched a new website due to the growing popularity and use of HDD Fan Control for people wanting to install hard drives and SSD’s in their iMacs, or those that have already done and experienced the loud fan noise.