@Lost_N_BIOS:
The related mainboard has 4 different on-board Intel SATA Controllers, which are activated/inactivated by the BIOS depending on the SATA mode setting:
1. IDE mode: "Intel(R) 8 Series/C220 Series 4 port Serial ATA Storage Controller" (DeviceID: DEV_8C00)
2. IDE mode: "Intel(R) 8-Series/C220 Series 2 port Serial ATA Storage Controller" (DeviceID: DEV_8C08)
3. AHCI mode: "Intel(R) 8 Series/C220 Chipset Family SATA AHCI Controller" (DeviceID: DEV_8C02)
4. RAID mode: "Intel(R) Desktop/Workstation/Server Express Chipset SATA RAID Controller" (internal DeviceID: DEV_????, external DeviceID: DEV_2822)

@tuc47:
After your time consuming and totally unsuccessful tries to switch the SATA mode from within a running OS you should be happy, that you finally got XP properly installed in AHCI mode. Additionally you have now a clean and performant OS without any data garbage from the last years.
If you should be still unhappy and insist trying to get your old XP running in AHCI mode, try whatever you want, but I stop my support at this point.
As I had already written previously: The best and safest way to get Windows XP properly installed onto an Intel chipset system in AHCI mode is to follow >this< guide, but you obviously prefer other options.
Good luck!