That can't be artifacting. He's posted a Windows screenshot, and the dots are showing up in the screenshot. That means that Windows is actually rendering those dots since a screenshot bypasses the display path of your graphics hardware; they're not an artifact of an overheating GPU or bad VRAM. In other words, it's a software problem.
My guess would be some type of 3rd party program installed which is trying to alter the display, which is adding the dots. Try booting into safe mode and see if the dots still appear. If they're gone, then you're going to have to go through the list of programs and utilities which normally load when the computer starts, and figure out which one is the culprit.