Your crashes are graphics card related, so if changing graphics cards, clean installing Windows, and temperature monitoring do not help, it is likely the motherboard at fault. Other causes could be power supply, memory, or your monitor. Have you tried a different power supply? What about running with different RAM? Different monitor?
Before you proceed with the following, answer these two questions: Are you still under warranty? Does your warranty allow you to open up the machine to check hardware?
If you are unsure of the answers to these questions, contact your system manufacturer. WARNING: The steps that follow can void your warranty!!!
Strip down your system to run only the bare essentials: one RAM module, the CPU, motherboard, one hard disk, one graphics card (or use onboard graphics if you have it), keyboard, mouse, and one monitor. See how the system behaves by running Windows for twice as long as it typically takes for you to get a crash. If it is stable, add one piece of hardware back at a time until you get crashes again. Take notes of what hardware you add and how the system responds to the hardware changes. As you add and remove hardware, follow these steps for ESD safety:
- Shut down and turn off your computer.
- Unplug all power supplies to the computer (AC Power then battery for laptops, AC power for desktops)
- Hold down the power button for 30 seconds to close the circuit and ensure all power drains from components.
- Make sure you are grounded by using proper grounding techniques, i.e. work on an anti-static workbench, anti-static desk, or an anti-static pad. Hold something metallic while touching it to the anti-static surface, or use an anti-static wristband to attach to the anti-static material while working. If you do not have an anti-static workbench, desk, or pad, you can use your computer tower/case by finding a metal hold in it, such as a drive bay.
Once these steps have been followed, it is safe to remove and replace components within your computer.