Windows XP is a LOT pickier about what it considers ACPI compliant than Win98, and even Win2000. Case in point, my Asus P2B-F installed perfectly as an ACPI board under 98 and 2000, but in XP I had to modify the TXTSETUP.SIF file to force an ACPI install.
If you're determined to install ACPI under XP, here's some required reading:
I've found that all Award BIOSes dated July 1994 or later correctly support the LBA assisted translation up to the 8 GB limit. There is however a bug in the BIOSes dated before January 1996 that limits the harddisk size display, on the BIOS Setup and boot screens, to 2015 MB. Whenever a drive is 2016 MB or larger, the display starts to count from zero again. The same happens at 4032 and 6048 MB. ...