Windows 10: BSOD various stop codes, unable to boot past post even w/ safe mode

The problem started when a game froze, and I did a hard reboot of the computer. Since then every boot attempt crashes after the BIOS screen, even when trying safe mode and even with a brand new hard drive and clean install of Windows 10. I'm completely unable to boot to windows so I am unable to post a dump file or any other file from the machine. I can boot into the blue repair screens using a Media Tools thumb drive, but that's it. And even that often crashes.

My specs:
MSI Z170a gaming 7 motherboard
Skylake cpu
2 sticks of 8 gig ram
Geforce GPU (don't remember the exact model)
Samsung Evo 500 gig SSD (and now a brand new second one)
Networking & sound is built into the mobo

Here's what I've done so far:

• Updated BIOS, flashed, and reset CMOS (repeated several times)
• Tried booting in safe mode = crashes in the same place, same way
• Using Media Recovery Tools on thumb drive, I've tried rolling the OS to every available save point = says "unable to refresh"; tried repairing, says "unable to repair"; tried resetting, says "gathering files" and then crashes
• Tried various command prompts recommended in forums (e.g. bootrec) = no change
• Weirdly, bootrec /rebuildbcd = says completed successfully / "total identified windows installations: 0" -- that isn't right, is it?
• Pulled out RAM, tried different slots and different configurations = no change
• Ran Memtest for 15 passes = no errors found in RAM
• Pulled out GPU and replaced it with GPU from another machine that works = no change
• Visual check of mobo for damage, tried a swapping out a few wires = no change
• Took out old SSD and connected brand new SSD, ran clean install using recovery thumb drive. That made the system more stable. I was able to consistently boot to the login screen (whereas before it would crash unpredictably), but it still crashed with BSOD every time after login. Still unable to boot to safe mode.
• Foolishly, I tried to reinstall windows on that new drive. It crashed half way through, and now the drive also can't boot reliably even to post.

So here are the questions I would most like help with:

• The obvious culprit is bad/corrupted drivers, but shouldn't a brand new hard drive with a clean install fixed that? Are there drivers (other than bios) that live in the mobo that could be corrupted?
• Is it possible this is malware? I had no indication of a problem before this sudden catastrophic failure. And again, wouldn't a new hard drive with a clean install have booted? The old drive was fully disconnected when I did the install.
• If this is hardware, is it either the mobo or the power supply? (Ram tested fine, swapping out the GPU didn't change anything, and new hard drive didn't change anything -- those are the only extra cards I'm using.)
• Is there anyway to reliable test whether the mobo is bad w/o replacing it?

:)

 

SYSTEM THREAD EXCEPTION NOT HANDLED

I'm afraid I am completely unable to get to the desktop GUI, the BSOD appears even in Safe-Mode.

I might be able to boot straight into CMD and I do have other computers on the LAN.

 

Inaccessible boot device

Unable to get past step 1 . Tried both safe mode and safe mode with networking. Goes back to inaccessible boot device.

 

Hello and welcome to tenForums *Smile

Without any files to analyse there is not a lot that we can do in this section of the Forum. Maybe you can get better help in the General section. In the meantime I would point you to the following thread which provides a tool for investigating this:
Windows 10 Recovery Tools - Bootable Rescue Disk

 

Try removing half the ram, see what happens. If no change swap removed and installed ram.

 

It was the motherboard. Swapped a new one in & now it works fine. At least so far. Thanks everyone for the support.