I thought I might once again try booting to the Windows Repair Console and try some of the rather severe repair options there, like fixmbr and fixboot. Heck, if nothing else, I could do a brand new "bare metal" installation on that drive. But when I tried to boot from the CD-ROM, something odd happened. It displayed the "checking your hardware" message, then went to a blank screen and never finished loading the Repair Console.
I shut the machine off, inserted the (working, will boot) 120 GB last-ditch backup hard drive, and then attempted to boot from the CD-ROM. This time it worked and would go to the Repair Console, not that I actually need it for this drive.
This is very strange. I'm trying to figure out what sort of hardware failure would cause both of the 160 GB drives (from different manufacturers, even) to fail in such a way that WinXP would hang when booting from CD-ROM. I suppose I could contact Dell tech support -- the machine is on an extended service plan -- but I doubt anything that happens over the phone or e-mail or chat with someone in India is going to help. The question is whether I'm patient enough to wait them out until they agreed to dispatch someone to come look at it.
I actually need to open a call with them anyway, because I probably should have the screen replaced on that drive, and the keyboard on the other one. It is more efficient, I would think, to do all of the repairs at once, but I have a feeling that their system will want to treat them as three different calls and thus dispatch either three people or the same person three differen times.