How to forcibly disable (spin down) an internal Hard Drive (Windows 10 v1903)
I will answer how I managed to find a solution. Note that it doesn't have to work for you, it does on my Windows v1903 machine with Toshiba P300 hard drive.
- Download Windows v1607 .iso (https://tb.rg-adguard.net/public.php)
- Extract "SATA AHCI Controller" and "DiskDrive" drivers from the v1607 Windows
- Install the old drivers, I assume they work for any version above v1607.
- Use software called HotSwap! to spin down the drive (it does that after ~5s). So far, after 3 days of testing, the HDD doesn't seem to spin up by itself. Even when launching software like HWInfo, CPU-Z, or CrystalDiskInfo. The only way to make it active again is by doing "Scan for hardware changes" (you can do that with DevCon Rescan/Device Manager).
I've uploaded the v1607 drivers HERE. In order to install them you need to disable "Signed Driver Enforcement", since for some reason they don't seem to be signed by Microsoft once you export them. If you don't trust a random guy on the internet (and you shouldn't) then do it yourself.
You can export the drivers with just 7zip and the .iso. You'll be looking for 2 folders called "mshdc.inf_amd64_67bad2c7196330b6" and "disk.inf_amd64_1e7038548624f167" located in: Win10_1607_x64.iso\sources\install.wim\1\Windows\System32\DriverStore\FileRepository\
Edit: The solution randomly stopped working after a few days. Seems like I underestimated how awful Windows is.