So you mean AHCI and sata mode are one and the same. Then why isnt it support in WINDOWS XP (even in SP3). AHCI is supported only under windows 7 natively....
Also is there any benefit in using AHCI mode rather than SATA mode ?. Any disk performance especially in booting and file transfer speeds ?
native support for SATA HDD's started from windows 7. windows xp natively did not have any drivers to support SATA HDD's. if you wanted to install xp in SATA mode during a fresh clean install, either you need to have a floppy disk drive to load the drivers from it after the setup loads, or you need to embed the driver into the installation itself which can be done using free softwares available online.
OR
there is a tutorial here on TE which explains how to switch your existing windows xp to start using your HDD in SATA mode. it requires a registry edit and installation of the driver for SATA.
and yes, in SATA or AHCI mode, you will not only get better transfer speeds, but the overall performance of the HDD improves as the input and output of data is managed more efficiently.
* And once the registry edit is done in XP, you need to restart and switch your HDD mode to SATA from your BIOS menu.
a very good software which i used to insert the SATA drivers in the XP installation was nlite. you can directly insert the drivers in the image of the XP setup, or any other drivers that you like and softwares too, so that when you install that version of xp, everything is installed by default.
its very useful to make a setup for your rig, so that when you format your pc, you need not install any drivers separately. you can just insert the drivers, and when you install, all the drivers are installed along with it.