Please see canned info below;
Download Display Driver Uninstaller DDU from here
Create a new folder on your desktop and name it 8400GS drivers, download and save to your new folder the latest drivers for your card from here create a new restore point, uninstall the drivers for your present card using the DDU, restart the computer in Safe Mode only (no networking) install the saved drivers for the new card, restart and test.
Avoid using any software that automatically updates your system.
Please note that drivers should never be updated unless it is to address a known issue, if a driver is installed needlessly you can end up creating the very issue that the updated driver was intended to correct, rolling back to the previous driver does not always work and waiting for the next driver update can take some time and may also not resolve the issue.
Where possible, always obtain drivers directly from the provider of your hardware/software and only use drivers or patches from third parties for older or no longer supported hardware/software.
I probably won't buy any more Nvidia products.
Can I ask why, I favour neither Nvidea or Radeon so no bias here but I feel that you would be acting rather hasty in deciding not to purchase Nvidea products ever again, you said yourself in your OP that it was Windows that 10 tried to update the Nvidia 8400GS driver not Nvidea, also worth mentioning is the fact that unlike certain other brands at least Nvidea are still offering support for a video card that is potentially seven years.