I'll back up what abomally said with my personal anecdote. I've had a graphics glitch where a polygon on an item/character would suddenly throw colored streaks across my screen. I could reset it by reducing graphics to best performance then going back to my original setting. No amount of game updates, driver updates, OS reinstalls would fix it, nor would other games or software/stress testing reproduce it. My GPU had a very aggressive factory overclock that was known to be at the limit of what that specific chip could achieve. I've updated to a new GPU last month... guess what... the glitch hasn't come back since. Another point about overheating. Not every component in your computer that is heat sensitive actually has a temp sensor on it. My old GPU for example, never overheated. But the glitch happened more often on hot days. I've long suspected that some other component was overheating; GRAM or VRMs maybe... don't have a thermal camera so I could never prove it. In my experience, RAM is another component prone to give strange errors in specific circumstances that is hard to diagnose and reproduce. The hours of my life I've wasted troubleshooting with software, only to fix the problem by removing the offending stick. My point is, I agree with abomally in that certain hardware problems are very, very hard to pinpoint.