I would have liked to choose a more explicit title, but the truth is I'm having a hard time putting this into words.
So I turn on my computer (which was completely cool) and start my favourite video game (Chivalry: medieval warfare, which I have been playing for a while without any problems) and I instantly crash to the desktop. I then retry my game and am rewarded with a very colourful crash: my main display shuts down and my secondary starts displaying colours in a very strange and pixelised pattern.
Every time I restart my computer, the booting up phase is riddled with stray pixels going berserk in random patterns, until I get to the point where I should see my desktop, which is instead replaced with a blue screen which automatically reboots my computer.
I tried opening up my computer. My GPU was pretty dusty so I cleaned it out and replaced it in its slot. All this to no avail.