Hello Folks,
I fixed the problem. It turns out that the newer drivers were confounding the hardware. I switched from ATI drivers to OMEGA drivers, then worked backwards until I found a version that seemed to work well for me, rad_w2kxp_omega_38221. I suspect with some tweaking I can get a newer version to work.
I have tested with some downloaded games from the website, and have tested with SED and small.c (works), and with MED (works).
Happy, Happy.
--Peter