Originally Posted by Supershanks 
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 isn't an option.
3) The only previous way round this was to select the required sata access & then reinstall windows.
Think you've missed the point of my post mate
I initially installed XP Pro with the drives connected to the Jmicron/GigaRAID ports on my DS3P, these were set to run in normal IDE mode. I then enabled AHCI on the ICH8R ports so the drives were still connected to the GigaRAID ports. On boot up XP finds new devices so I installed the drivers and did a reboot, then shutdown and moved the drives over onto the ICH8R ports which are now running in AHCI mode.
The reason I did the above was I didn't have a floppy disk drive on my rig at the time so couldn't do the F6, install drivers thing. I've actually done the above now twice as I reinstalled the OS for different reasons and it worked both times.