I found a workaround to boot windows after changing to AHCI easily.
I wasn’t able to make it work (no troubleshooting in the page worked) until I manually setup a safeboot minimal mode with an elevated cmd right after I changed the registry values.
Apparently the regedit changes for the “ RST enabled, Windows installed” scenario were being reset on the first fail cycle, so when entering repair mode they wouldn’t get loaded. I’ve read somewhere that the StartOverride changes only lasts for one boot cycle.
The solution was to set the safe mode (safeboot) manually. Right after the regedit changes:
- With a cmd with admin rights (windows search: cmd, then right click, run as admin):
bcdedit /set {current} safeboot minimal - Reboot to BIOS.
- Change from RAID (RST) to ACHI in the BIOS.
- Reboot.
- Windows enters safe mode correctly and setups the “new” hardware using the temporarily enabled drivers. New hardware connected sounds and all.
- Then before restarting, revert the safeboot mode:
bcdedit /deletevalue {current} safeboot - To go back to normal boot.
Tested with a Dell XPS 13 7390 (model P82G)
Also found a typo: The activate diskpart command should be changed to active (and add a note that it might fail with an error message about the volume not being “Fixed MBR”)