If you have the SATA disk set AHCI mode, XP does not contain native SATA drivers that support AHCI modes.
You have 2 choices.
1. Set the SATA controller to "Native or IDE Mode" in the BIOS. This will not allow you to use some of the advanced features of an SATA drive, like hot swapping drives, but it will allow XP to work with the drive without installing SATA drivers.
2. Download and install the SATA driver package for XP from ASUS as the above post suggests.