... because I blew up the malfunctioning hard drive. Literally. I powered on Curmudgeon's PC, there was a spark, smoke came out of the vicinity of the spark and then all was silent. After I powered the PC down I took the offending, smoke-emitting drive from the chassis and found molten slag on top of an IC. The slag was still smoldering. Nearby was another IC with a pit blown out of it. I surmise that the slag came from that pit.
Root cause analysis of the spark determined that I managed to somehow overcome the keying on the MOLEX->SATA power connector -- ultimate I was putting +12VDC on the pin that was expecting +5, I was putting +5 VDC on the pin that was expecting +12 and I swapped the grounds around too (the ground-swapping was the least of this drive's worries). If what I'm saying doesn't make sense, look
here. In short, "I made the yellow go to red and the red go to yellow," because I am a complete idiot. Fucking good thing I took a snapshot with Acronis of the drive before I started all this effort or Curmudgeon would be well and truly boned by my ineptitude.
I am not a happy camper.
I'm going to bed now. If I'm very lucky I won't accidentally cause the bed to explode, or something.