Had a customer in Phoenix who refused to believe his computer was just dusty.
He brought in a gaming rig that kept shutting off, convinced it was a virus. I opened it up and showed him the quarter-inch thick dust mat on the CPU cooler. He looked me dead in the eye and said, 'That can't be it, I paid $2000 for this thing, it should just work.' I cleaned it for free, booted it up, and it ran fine. Ever have a client just REFUSE the simple fix?