Well there wasn't really enough info in the release notes for that BIOS to gain my trust that it was the correct BIOS..... I've just accepted the probable fact that I'm probably just never going to find the correct BIOS update for this board. so I solved my issue by limiting the capacity of the drive to 136GB using Seagate Seatools
The problem I was having was that Windows XP would recognize the full capacity of the drive without any problems even though the BIOS was not seeing the full capacity and was limiting it to 136..... As I said, Windows XP had no problems *seeing* the full capacity, but because it detected that something wasn't right with the BIOS reporting it differently, it would only allow the drive to run in PIO mode..... with "blazing" transfer speeds of a WHOLE 3MB/s.
After limiting the drive in Seatools, resetting the IDE controller in XP by uninstalling/reinstalling it in device manager, and repartitioning/formatting the drive to it's new capacity, it's now working much better, with sequential reads of around 85MB/s, and sequential writes of around 30MB/s