Hello,

I have not seen a post that talked about this ... (but it is possible that I have not seen)

Because my Mac Pro 2008 has no BIOS (BIOS is emulated and AHCI is disabled) it's not possible to mod BIOS !

But i't's possible to modify MBR for activate AHCI with OSX/Linux scrip found here

Or it's possible to load GRUB and change device ID before Windows Boot :
http://darkfader.blogspot.fr/2010/04/windows-on-intel-mac-and-ahci-mode.html
My ESB2 SATA in ide mode has Device ID 2680
In AHCI mode : 2681
In Raid Mode : 2682

In GRUB you can change ID 2680 by 2681 (by this command) :
setpci -d 8086:2680 90.b=40
lspci command (should now show 2681 instead of 2680) !

Same for Raid :
setpci -d 8086:2680 90.b=80
lspci command (should now show 2682 instead of 2680) !
In my case, I did not Raid ROM and Raid mode does not work.

Apparently the command remains the same for Intel ICH6/ICH7/ICH8 controllers (just change the device ID). This should also work on PCs (But I have not tested).
For intel 3400 chipset: setpci -d 8086:3b28 90.b=60
http://forum.osxlatitude.com/index.php?/topic/2116-dell-d820-ssd-support/page-2
http://forum.notebookreview.com/threads/ich7-m.460478/

For Nvidia : that is not documented and for AMD I do not know ...
Except MCP79 : setpci -d 10de:0ab5 9c.b=06

MCP79 BIOS only SATA (AHCI is disabled)

SATA PCI ID VEN:10DE DEV:0AB5

no driver for winxp ?