Does it stop spinning of the hard disk? If I didn't open any new prog or write any data, will it start again? I'm asking it because my hard disk getting very hot due to summer heat. As most of the time, I'm reading pdf books on pc. I want to shut down HDD. Do you know any good alternative?
It means that disk would stop completely after predetermined time with no action. It also is not only for specific disk but all disks in the system. That makes them all start up at same time so it's pretty useless and also introduces delays in accessing files and in some cases may slow down whole machine until it spins up again while doing self check.
Only got one hdd. If it stops spinning, windows stops. You'll only see that in deep sleep modes, not when the pc is active. Even at idle, the pc is still active, deep sleep is a few hours after not touching the mouse and keyboard.
Having adequate airflow is the only viable solution, and even then pc parts won't be any cooler than the ambient temps. Expect case temps with good airflow to be @ 6-12°C higher than room temp. That includes anything inside the case being that temp too. If your airflow is sadly lacking or seriously compromised, expect higher case temps.
Just as an addendum, it doesn't stop the drives if you are using them just because the time limit came up.
Also, there used to be a bug in intel RST fro win10 that broke this and switching to the MS AHCI driver caused the drives to spin-down independently again; otheriwse it was an all or none (usually none since C: is almost always in use by the OS). I don't know if that was ever fixed.