The ultimate solution is by using OEM Windows XP CD which comes with your system, which usually has built-in appropriate driver for S-ATA harddisks running in AHCI mode. However, if you lose or do not have the OEM XP CD, or is given Windows 7 DVD but decide to downgrade to XP, there are 2 options to install XP from scratch.
You can also update the BIOS from HCL official website if they permit it and maybe you'll have the ATA/AHCI option in your BIOS.
Make sure to obtain the BIOS upgrade software from a reliable source. Downloading a BIOS from sources other than the manufacturer's web site is risky. For example, versions from the same BIOS software developer for one manufacturer's motherboard may not work on a different manufacturer's motherboard. Using the wrong BIOS or version might "brick" the board, thereby requiring either a BIOS replacement or reprogramming of the BIOS by the manufacturer and rendering the computer unable to boot until that is done.
Make sure the electrical power source is reliable when flashing a BIOS. Any sizable fluctuation or loss of power during a flash process can corrupt the BIOS. Therefore, never power down or reset a PC when flashing the BIOS. If flashing the BIOS from a booted OS, first disable all unnecessary applications and background processes.
Avoid updating the BIOS unless you know exactly what you are doing. Failure to follow a manufacturer's directions and precautions may corrupt the BIOS as well
If you don't know where you go, get back where you come.......