Computers OS (windows 10) completely freezes during games?

This is second time to post this i still more information nothing iv done has solved it
I'm totally lost to what this could be. Before I begin this happened with my old gaming computer so replaced most of the parts mostly everything.

During any game doesn't matter which game it is could be (anno 2070, Skyrim, minecraft, MGS5) the whole OS just freezes randomly not a set amount of time during games.

Does anyone know 100 percent what causes this I looked online and can't find a definite answer people say (falling HDD, corrupted OS, GPU is faulty, processer is damaged)

Firstly my OS windows 10 is a fresh instalment, the GPU is new, the motherboard is new, the Cpu is new, the OS was freshly installed on my new SSD, so basically is a new computer but for 2 parts

The only 2 hardware which I didn't replace was the RAM 2 slots of DDR3 4GB and a power supply corsair CX750M (750wats) i did memtest for the RAM (so many tests took ages) couldn't find a problem with the RAM.

Please for the love god (or for the love of Talos) help me I'm completely lost at this point

Processor: AMD FX(tm)-9590 Eight-Core Processor (8 CPUs), 4.7GHz
Memory: 8192MB RAM
Available OS Memory: 8088MB RAM
Operating System: Windows 10 Home 64-bit
Card name: AMD Radeon (TM) R9 380 Series
Manufacturer: Advanced Micro Devices, Inc.
Display Memory: 8118 MB
Dedicated Memory: 4073 MB
Shared Memory: 4044 MB
Chip type: AMD Radeon Graphics Processor (0x6938)
Update: my PSU is corsair CX750M

Added (1). and when i say completely freezes i mean the OS freezes, mouse and keyboard doesn't respond have to hold down the power button to turn it off then restart the computer.

Added (2). water cooling system

Glen I answered you earlier you have to try to break down the problem by what I told you earlier on, it can be a lot of things unless you don't try to diagnose the problem you wouldn't get through try reinstalling the OS Try something.

I'm not sure what to try the only other thing i can do is to just replace the last 2 components the PSU and the 2 RAM chips i took out 1 slot each time before problem still happened

At least this time you told about the power supply.
You tell nothing about MB, and CPU cooling fan, so I'm guessing something is wrong there.
Try more cooling.

Windows 10 like its buggy little brother Windows 8 is intended to NOT run Older Games (those not programed for it).

Games Do NOT like Shared video memory:
"Skyrim" wants…
- Windows 7/Vista/XP PC (32 or 64 bit)
- Quad-core Intel or AMD CPU processor
- 4GB System RAM
- 6GB free HDD (Hard disk drive) space
- NVIDIA or AMD ATI video with 1GB RAM:
Nvidia GeForce GTX 260 or higher;
OR
ATI Radeon HD 4890 or higher
- DirectX 9.0c
DirectX compatible sound card
- Internet access for Steam activation

Minimum System Requirements*
-Windows 7/Vista/XP PC (32 or 64 bit)
-Processor: Intel Dual Core 2.0GHz or equivalent processor (AMD Sempron @ 2.4 GHz)
-2GB System RAM
-6GB free HDD space
-Direct X 9.0c compliant video card with 512 MB of RAM
-DirectX compatible sound card
-Internet access for Steam activation
*Minimum Specs, sell games, but may not make for satisfying game play.