DPC_WATCHDOG_VIOLATION Windows 8.1 Nvidia Drivers Issue

UPDATE: Turns out the probelm was a Windows Security Update. I uninstalled the three latest windows updates as of today and now my PC is fine.

Hi all, last week I started getting a BSOD when watching videos and playing games. The error code was DPC_WATCHDOG_VIOLATION. Using WhoCrashed it looks like its a problem with Nvidia drivers. Here's the log, these two messages appear for every crash.

On Tue 2/6/2018 12:40:50 AM your computer crashed or a problem was reported
crash dump file: C:\WINDOWS\MEMORY.DMP
This was probably caused by the following module: nvlddmkm.sys (nvlddmkm+0x28692b)
Bugcheck code: 0x133 (0x1, 0x1E00, 0x0, 0x0)
Error: DPC_WATCHDOG_VIOLATION
file path: C:\WINDOWS\system32\drivers\nvlddmkm.sys
product: NVIDIA Windows Kernel Mode Driver, Version 390.77
company: NVIDIA Corporation
description: NVIDIA Windows Kernel Mode Driver, Version 390.77
Bug check description: The DPC watchdog detected a prolonged run time at an IRQL of DISPATCH_LEVEL or above. This could be caused by either a non-responding driver or non-responding hardware. This bug check can also occur because of overheated CPUs (thermal issue).
A third party driver was identified as the probable root cause of this system error. It is suggested you look for an update for the following driver: nvlddmkm.sys (NVIDIA Windows Kernel Mode Driver, Version 390.77 , NVIDIA Corporation).

and

On Tue 2/6/2018 12:40:50 AM your computer crashed or a problem was reported
crash dump file: C:\WINDOWS\Minidump\020218-39328-01.dmp
This was probably caused by the following module: ntoskrnl.exe (nt+0x154EA0)
Bugcheck code: 0x133 (0x0, 0x501, 0x500, 0x0)
Error: DPC_WATCHDOG_VIOLATION
file path: C:\WINDOWS\system32\ntoskrnl.exe
product: Microsoft® Windows® Operating System
company: Microsoft Corporation
description: NT Kernel & System
Bug check description: The DPC watchdog detected a prolonged run time at an IRQL of DISPATCH_LEVEL or above. This could be caused by either a non-responding driver or non-responding hardware. This bug check can also occur because of overheated CPUs (thermal issue).
The crash took place in the Windows kernel. Possibly this problem is caused by another driver that cannot be identified at this time.


The thing is, I didn't update my drivers or anything before the crashes started happening, they just began out of nowhere. Sometimes my PC is fine for a day or two, sometimes it crashed every 10 minutes. I've tried every solution on the web so far, including:

Messing around with power settings
Updating my drivers
Uninstalling Nvidia drivers with DDU and rolling back to several previous versions, which doesn't help, I still BSOD
Updating BIOS (couldn't, as I have an old mobo with no new BIOS since 2014)
Running chkdsk
Uninstalling Nvidia Audio Drivers
Swapping out my GPU for a different one (also Nvidia, and it also crashed with the same error)

That last one leads me to believe that it's not an issue with the card, but some other component. I've run memtest86. FurMark, and Prime95 tests with no errors. The only thing I can think of is that something might be wrong with the hard drive I have Windows on, as it is 5 years old. I have ordered a new drive and will be replacing it, but in the meantime I'd appreciate any suggestions. Thanks.

Specs:
Windows 8.1
CPU: AMD FX-8370
GPU: GeForce GTX 970
Mobo: Asus - M5A78L-M LX PLUS
RAM: Kingston HyperX FUry Red 8gb
PSU: EVGA 450 BT 450w
Two Western Digital Blue 1TB Hard Drives