I have my optiplex 755 working in legacy mode and I installed all the drivers from the resource cd but when I try to put the bios back to AHCI raid auto detect mode, xp sp2 will not boot. How can I force windows to accept the right driver so it will boot with the AHCI setting in the bios? I have a fully bootable and working machine in xp but only in legacy. I'm on BIOS A04 which is the latest.