Showerthought: a bad RAM stick ate 6 hours of my life because I trusted the BIOS beep codes
Client drops off a Dell that won't POST, I hear the beep pattern, assume it's the GPU, swap cards for 2 hours, nothing. Turned out one stick in a 4 stick kit went bad and the board was throwing a code I had never seen on that model, so I chased the wrong part all afternoon. I finally pulled each stick one at a time, found the dead one in 10 minutes, and felt like an idiot for not doing that first. Now I always start with RAM on no-POST jobs, even when the beeps point somewhere else. What's the longest you've chased a wrong code before just pulling parts one by one?