I have to agree that I can't see a logical reason why an installation program should cause the near-catastrophic problem I described. I'm still suspicious there is a connection, but I can't prove it. I am NOT about to repeat the process to test any such hypothesis, so that question will remain forever unanswered.
Early on I had pretty much ruled out BIOS setting changes and cable failures. But my problem HAS now been resolved. My initial call (online chat) to any technical support was to Cisco/LinkSys. That got me nowhere, except to realize that the particular rep I was trying to communicate with was paying no attention to what I was saying. The next attempt was with Dell--this one could be described as "close, but not cigar." The first suggestion from that rep was that I needed to clear NVRAM; it turns out he was right, but unfortunately he did not know the necessary steps to take on this particular Dell model. Yesterday I finally happened to run across a discussion on Wilders Security Forum about someone else's similar problem. I performed the NVRAM-clearing steps described in that discussion; lo-and-behold, upon the next power up I regained access to all my internal mass storage devices. Those steps are: remove ALL power (AC and battery) and hold the power button in for 20 seconds. I am now hastening my migration away from this computer, hoping to complete such migration before happens again.
