An unfixable problem.

I already wrote here about this problem months ago. I tried everything, and I mean everything. It drives me mad.

It's hard to explain the diagnosis. After an uptime of about half an hour, when I perform an action, like closing a window, closing a tab or switching a window, the system will be stuck and the current output sound will be looped and irriating for a fraction of a second.

It occurs in both Windows and Ubuntu (which are installed on two different Hard-Disk Drives); in both my old motherboard and my new one; in both my old CPU and my new one; in both my old RAM and my new one; and in both my old PSU and my new one.

I don't have any idea about what to perform next.

Is the video card working when monitor is off? Because it happens also when monitor is off.