Windows 2000 and UDMA66

I am running Windows 2000 server,Cannot get Udma to work with my Quantum fireball lct harddrive.I have a sis 620(I know not very good but its what I have).I have UDMA enabled in the bios but have tried with it disabled.I am using UDMA cables.I only have the one drive on the primary channel.Have tried the siside patch that is supposed to fix the problem but still reports pio mode.I have also tried editing the registry adding enableudma66 as is necessary for some chipsets but still does not work.This machine also has win98se on it and udma66 works fine when I boot to it.Have the latest drivers as far as I know.Any suggestions?