XP install does not include the AHCI drivers unless you add them (slipstream) to your installation disk. They are, however, provided by your mobo manufacturerhttp://www.gigabyte.com/products/product-page.aspx?pid=4140#dl
Select XP 32/64 bit
Save the Driver file to, say, desktop.
Set a System Restore Point (just in case)
I believe the downloaded file is self loading, just run the Setup...
Go to Device Manager and locate your SATA Controller in IDE ATA ATAPI Controllers.
Double Click, and choose Driver Tab and Update Driver/ Install from Location.
Point to Desktop and Drive Folder Location.
Hope it works!