SATA - AHCI vs compatibility mode

I installed XP in dual boot mode with Vista pre-installed on a Toshiba Satellite L350-20J notebook.

Since I couldn't find the appropriate files for the F6 process in the Matrix Storage Manager (in the L350 Toshiba driver section for XP, you get an EXE file) to use at xp install time, in the BIOS I switched the SATA AHCI parameter to "compatibility". The XP installation went fine.

Once XP was installed, when I tried to run the Matrix Storage Manager driver, I got the message "This computer does not meet minimum requirements for installing the software". On the other hand, the chipset utility was installed without a hitch.

When I switched back the "compatibilty" parameter to AHCI in the BIOS, the system would not boot properly. It would direct me to multiple choice screen for Safe mode, etc.

Furthermore, EasyBCD gets stuck when I try to define Vista in the Add/Remove entries section, when in compatibility mode.

How can I get into SATA mode at this stage?