HL90 and XP Installation Guide:
 
1. By default, AHCI is enabled in the BIOS and there is no option to change it.  You will need to disable AHCI first in order to install the Windows XP OS.  To disable AHCI, you will need BIOS 1.03 or higher to work with the Compal AHCI utility tool. 
 
2. Update the BIOS to 1.03 or higher and have a bootable floppy diskette (if you have external floppy drive), a bootable USB flash drive, or a way to create a bootable CD handy.
 
3. Unzip NB-317-101 AHCI.zip to a folder and copy the files (AHCI_DIS.EXE and ReadMe.txt) to a bootable floppy diskette, a bootable USB flash drive, or use your burning software to create a bootable CD out of it.
 
4. Boot from the bootable device by pressing F12 during initial boot and select the bootable device, which contain the AHCI_DIS.EXE.
 
5. At the DOS prompt, type AHCI_DIS then press ENTER.  You will see a message indicating AHCI was disabled successfully. Next, reboot and insert the Windows XP installation disc to the optical drive. Press F12 during reboot and select boot from optical drive to install Windows XP as usual.
 
6. After the Windows XP installation is finished, continue on installing drivers and applications.  You can use the bundled drivers disc but the drivers disc does not have a Windows XP drivers menu.  Do not panic because most drivers from the Vista menu work fine on Windows XP, except for the following drivers and applications: 
Driver Support:

nVIDIA VGA 
LAN 
CIR 
 (Use the Vista32 drivers from the CD driver disc for the rest of the device drivers) 
MeetingSecretary, SafetyGuard, and EntranceGuard does not support Windows XP 