Shutdown does not 'Poweroff' computer

Some system details:— home built system, ASUS P8Z77-V mobo with latest (2104) BIOS, 16GB RAM, Gigabyte NVidia GeForce GTX 650 Ti video card driving primary and secondary monitors, Gigabyte NVidia GeForce 210 video card driving monitor 3, 3 x 3TB HDD, 2 x 250GB SSD, 1 x 120GB SSD.

Currently triple booting W10 build 10049 and 2 (licensed) installations of W8.1 (one a work in progress to replace the main setup, which appears to have some (not vital) corruption). Using the native boot manager tweaked with EasyBCD to set default. W10 is on the 120GB SSD.

When I use any of the methods to shutdown my windows 10 installation the video turns off, but the computer does not power off. I have set up a shortcut < shutdown.exe -s -f -t 0 > but that gives the same response, no power off. Using restart, the computer does power off and then power on again as expected.

Another, perhaps related, issue is that if I invoke sleep, and then resume several of the drives do not appear, and are not accessible. They do not show in Disk Management or File Explorer. While I am not now sure when this lost drive issue surfaced I think it was about the time W10 build 9926 was issued. It is not specific to W10, the W8.1 installs are also affected. A restart, which gives a 'cold' boot, restores the drive availability.

The 'not powering off' issue, as I remember, began later. And it also affects the W8.1 installations. So I began to wonder if it was a mobo problem, but the fact that the system does fully power off when restart is invoked kinda indicates that it is not a mobo issue. I've searched for answers without success. "Poweroff" is not a command recognized by Windows 10. I tried Sysinternals psshutdown, but that will not run if the < -k > switch is included (this switch invokes "poweroff" if available.) It runs without that switch, but doesn't power off, so the same result as all the other shutdown methods.

I have to force a power off manually to restart the system, as the shutdown process, as it is at present, leaves the system unresponsive.

I'm prepared to edit the registry, if that would provide a solution.

Thanks in advance.

Thanks, Shawn.
And thanks for the tutes you have posted. I refer to them often!
I should have mentioned that I had already disabled Hibernation, and turned off Fast Startup . I manually set the value of the HiberbootEnabled DWORD to 0 as well as ensuring that it was disabled under Power Options. I was a little surprised to see that the HiberbootEnabled DWORD was still set to 1 after disabling Fast Startup under Power Options, but perhaps I hadn't rebooted before looking in the registry.
I'm in W8.1 as I type this, and I see the HiberbootEnabled DWORD is set to 0 in the W8.1 registry, and I don't think I did it manually, or used your .bat file.