How to get correct result on "Read Native Max Address Ext"(0x27) command? (XP-SP2)

Hi all
i try IOCTL_ATA_PASS_THROUGH, and the ATA_PASS_THROUGH_DIRECT.CurrentTaskFile is correct information about HDD's native max address, but ATA_PASS_THROUGH_DIRECT.PreviousTaskFile are all zero, then ATA_PASS_THROUGH_DIRECT.PreviousTaskFile is valid if execute it under Vista, could any one know how to let my program works under XPSP2?
I'm sure my XP 48-bit mode is enable

TKS

Are you writing a driver? There's is a forum section for that topic.

Cheers!