A random sector of any screen in this pc renders this square artefact. Is a small portion of screen where squares render black in random position (of the screen or HMD). It can be in my left monitor, right monitor or oculus HMD. I change monitor, with or without oculus, with windows 7 and later windows 10 but persist over 5Yr. I has 2 GPU not in crossfire configuration and is not a gpu dependent (IS NOT A PARTICULAR GPU), since the monitor are in different GPU. The artifact renders on a top layer so if I record on screen the artefacts are not shown in the recorded video. But I can make a screenshot. I change 6 pay antivirus with no results. Independent from drivers update or CPU (i5 later i7). My GPU are two 7970. Any idea how to debug this or what can be?