Once the OS was up and running, then enable AHCI on the ICH8R controller, boot and install the drivers as requested by the OS
You appear to be uniquely fortunate.
The main point of this thread is to help many people who :-
1) install xp as you did with sata access set to the default IDE.
2) Upon enabling AHCI/RAID access mode in bios , any attempt to boot the os fails.
So
boot and install the drivers as requested by the OS
isn't an option.
3) The only previous way round this was to select the required sata access & then reinstall windows.