How to enable UltraATA 100 in Windows 2000 ?
W2000 and W2000 SP1 is only capable of UDMA66. You can install a patch to get UDMA100 support.
See Microsoft Knowledge Base Q260233 After applying this patch it may happen that harddisks report the current status as PIO mode 4 although the drive is running in UDMA100 mode.
See Microsoft Knowledge Base Q269555
Use latest release of drivers available by manufacturers:
VIA 82C686B available as Beta version at Soltek site