More followups:
The "pesky motherboard" may have been an unfortunate combination of flaky
power supply, rejected desktop case, and/or intermittents in the motherboard.
At times I could get the power LED to come on by shorting the power switch
leads to each other with a hard-drive master/slave jumper, but I also had to
resort to applying a reset the same way. Then I discovered (on one lucky
occasion when I succeeded in accessing the BIOS) that the BIOS had been set
to restart to the "last setting" after an interruption, and I changed that
BIOS setting to something less like a shell game. Often I got the power LED
light to come on by pressing down on one corner of the motherboard.
Eventually, after lofting the motherboard away from any chance of shorting to
the case, it wouldn't show any signs of life. Too many iffy situations. The
second motherboard got me off to a better start ... upon unplugging the
front-case-audio connection, the power came on once & for all.
I might try plopping that pesky motherboard on the kitchen table, and
supplying power, keyboard, mouse, spare hard drive, and monitor to see if it
will run, out of earshot of the FCC, with no case nearby. Hate to give up on
the thing - Intel's D865GLC motherboards have been good to me otherwise. The
others have survived my clumsy handling of them quite well. If I get a BIOS,
then I'll add the necessary CD/DVD ROM drive and proceed to shoehorn those
parts into another leftover case.
