After dealing with years of terrible decaying devices, I built a brand new shiny computer. Naturally, it must go bad.
Things had deteriorated to the point of crashing whenever a certain (very low) RAM allocation was reached. I grabbed a copy of memtest, and it stopped/crashed partway through a test. OK, definitely a memory issue.
Step two: get clever. I popped one of the RAM sticks out, and ran memtest again. Everything looks clean. Now I have a working computer. Do I leave well enough alone?
Step three: get too clever. I know I have a problem that’s fixed by pulling one RAM stick out of one slot. But! Maybe the RAM stick is bad, but also maybe the mobo slot is bad. Naturally I must do more experiments.
Out goes the good RAM, in goes the suspect stick into its slot. Now the computer doesn’t boot. Aha, I have learned something. Back in goes the good stick, but the computer still doesn’t boot.
So that’s just how things have been going for me.