Hi DevelSG,
I'm Dyari. Thanks for reaching out. I will be happy to assist you in this regard.
Since the computer works fine without the installed graphics card, it means the issue is from the graphics card which is whether hardware or software related.
If the issue is software related, kindly uninstall the graphics card driver completely using the DDU free tool:
https://www.guru3d.com/files-details/display-dr...
Then, install the latest driver provided on the manufacturer's website.
After that, run Command Prompt as administrator. Type this command and hit enter:
dism.exe /online /cleanup-image /restorehealth
Then, type this command and hit enter:
sfc /scannow
If you are overclocking your PC, try running everything (CPU, GPU, system memory) at their stock speeds. See if the issue is still reproducible. Or, turn off XMP profile or set it to Auto.
Download then install the latest version of BIOS & Chipset drivers from the manufacturer's website.
If the issue still persists, remove the graphics card on the motherboard and reseat it carefully. If its warranty still applicable, you can return it to the store.
Please do not hesitate to ask if you need further assistance.
Stay safe
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