The user who taught me to stop assuming the problem is hardware
Had a guy bring in a Dell Optiplex last month, said it was constantly crashing. I immediately started swapping RAM and checking the PSU. After about 2 hours and $150 in unnecessary parts, he casually mentioned it only crashes when his kids play a specific game. Turned out to be a corrupted graphics driver, not a component failure. He was an older IT guy, just sat there watching me work. When I finally asked what he thought, he said 'you always try the expensive fix first, don't you?' That moment made me rethink my whole diagnostic process. Now I always ask about software before cracking open the case. Any of you ever get humbled by a customer who knew more than they let on?