Checking the disk burners and external hard drives to the power strips to find out why some are working and some are not. This is taking time and patience. And I have to stand on a stool and follow the power cords from the peripherals to where they're plugged in. Seems like the top power strip is live and the bottom one is not.
No idea why. I follow the big, thick cords down to the power switch boxes, which I've pulled out as far as I can. It's a tight fit.
Ah. There it is. The "on" switch for the lower power strip, which has a couple of external hard drives and a disk burner plugged into it is labeled "speakers". I have it turned off since I don't want to listen to the speakers.
Flip it on. One by one, devices are added. Now the computer sees them all.