Well, the folks at Gig's offices got me out of the woods.

I will put them back on my buy list, with an unhappy face, since I
figure the board ought to come with the proper drivers, already on
diskette, and very clear instructions.

Anyway, the folks there emailed me a zip file with the proper driver
files. I unzipped them to a diskette.

You *must* install the drivers by hitting F6 during the windows XP
setup (according to what they told me.)

This board has a Gigaraid RAID driver, and you need to use their
gigaraid drivers, not the promise drivers talked about in many other
threads for some of the other boards.

After XP was set up, I went to the harware management stuff, navigated
to the disk drives, and TA-DA, the array was there, ready for
partition and format. Working well so far.