Well, I have been trying different things people have suggested, such as in this thread:
http://www.pcguide.com/vb/showthread.php?t=36004
I am learning a lot, but the behavior remains unexplained.
Again, nothing else seems to have any trouble seeing the HDDs connected to that Promise card ...except for Windows 2000 setup. Not a normally-running Windows 2000 or XP, not Windows XP setup, not booting to a DOS floppy, not booting to a Partition Magic floppy, not booting to a Norton SystemWorks emergency floppy, nothing .... very bizarre .....