Windows XP will only recognize an ACPI BIOS if it is listed in the \[GoodACPIBios\] section of the \I386\Txtsetup.sif file.
This process takes place during text-mode Setup.
You can alter this behavior by copying the CD-ROM to your HD or a network share and editing the \I386\Txtsetup.sif file.
The \[ACPIOptions\] section has an ACPIEnable entry, with the following possible values:
0 - ACPI is disabled at installation, regardless of the system BIOS.
1 - ACPI is enabled at installation if an ACPI BIOS is detected.
2 - ACPI is enabled on the basis of the GoodACPIBios list and the ACPIBiosDate. This is the default setting. The default ACPIBiosDate is January 1, 1999, so if your BIOS is newer, there should be no need to change this entry.
If you set ACPIEnable to 1, support for your ACPI BIOS will be installed, as long as the ACPI BIOS is detected.