I'm sure you are right, but I'd rather have more capacity than I need than be right on the edge of having not enough.

And it was the old power supply that failed. Possibly enabling ErP increased the startup load just enough to push it over the edge. A slight, lingering scent of burnt insulation was a clue. Or, maybe after eight years it was just tired and quit. Anyway, the computer now works quite well with the new power supply.

Of course, it wasn't that simple. I got the computer back, it worked fine, I could read email and look at files... but when I tried to type, I found I had no PS2, no keyboard. Interestingly, the keyboard worked just fine during bootup, I could go into the BIOS and change things, but as soon as Windows 8.1 started, no more keyboard.

If you Google for "Windows 8.1 PS2 keyboard not working" you'll get 172,000 hits. It is not an unusual problem, and I think I have an idea about what happened. I believe that the computer shop tested the computer after the power supply transplant using a USB keyboard. This article gives some insight about what that did...

I was mistaken in an earlier post in this thread when I said I had two 2TB drives. I have one 2TB drive and two 1TB drives, plus the SSD. The computer shop brought all of my old hard drives over into the new machine, not just the 2TB drive. So maybe a 600W power supply isn't totally overkill, particularly when I start firing up USB peripherals.

Anyway, the new computer now seems to be working the way I want it to. There are a few things about Windows 8.1 I don't care for, but I'll get used to them and probably grow to love them in the end.

tanstaafl.