You may need to update your BP6 BIOS - version RU is good for W2000 & Win-XP. You also need to get the Win2000 (works in XP) H/W driver, version 1.25 or later, on a floppy to be inserted when Win2000 ask for 3rd party drivers to be installed. Once the driver is loaded into the Win2K build you should be fine.
If this seems like too much work, do yourself a favor & go buy a Promise (Maxtor) ATA-100 (or -133) controller for $25-40. You will get native win2000 support & way better performance & reliability.
UDMA mode 4 is the fastest speed the HPT can handle, that is UDMA 66.
If your drive is capable of more, as i think yours is, then you won't feel the difference unless you buy an IDE controller card such as the promise one mentioned so often on this forum.