si_edgey According to Microsoft, however, Windows shouldn't do any kind of processing that would affect us, it's more likely to be the graphics drivers. But who knows!
This is incorrect. Microsoft often updates system files, including functions related to the display (especially DirectX/DirectDraw/DirectWrite)
I would reformat the PC, reinstall Windows, then block updates. You can put the Windows Update servers on your routers block list, that will prevent your PC from reaching them. There are lots of tutorials online