Windows XP enable AHCI mode after IDE Install

1. download the corresponding Intel Matrix Storage driver for your Motherboard (ICHX)

2. c:\iata_enu.exe -a

3. copy c:\Program Files\Intel\Intel Matrix Storage Manager\IaStor.sys c:\windows\system32\drivers

4. find the corresponding AHCI.reg file from the internet for your motherboard (ICHX)

5. load the reg file into you registry

6. reboot and enable AHCI mode

7. When windows started cancel automatic hard disk detection and install Intel Matrix Storage and reboot

taken from http://forums.hexus.net/hexus-hardware/112584-how-enable-ahci-raid-mode-without-reinstalling-windows-p35-ich9-ich9r-4.html