How to sort out problem if Ubuntu installer cannot see main C drive as boot device
Thanks, Andrew — that suggests the Ubuntu installer is currently only seeing your USB drive (e.g., SanDisk USB 3.2 Gen1) as a possible bootloader target, not your internal drive, which it should. This typically happens due to missing storage drivers, BIOS settings, or disk controller modes.
🧭 Here’s how to fix it step by step:
✅ 1. Check BIOS Settings
Reboot and enter the BIOS/UEFI setup (usually F10, F2, DEL, or ESC at startup).
Make sure:
- Secure Boot = Disabled
- UEFI Boot Mode = Enabled (not Legacy/CSM)
- SATA Mode / NVMe Mode = AHCI (not RAID)
If it’s currently set to RAID, Ubuntu might not see the internal NVMe/SSD.
⚠️ Warning: Changing from RAID to AHCI after Windows is installed requires registry tweaks in Windows before rebooting — I can guide you through that if needed.
✅ 2. Boot Ubuntu in UEFI Mode
Make sure you’re booting the USB in UEFI, not Legacy mode.
On the boot menu, the USB entry should say something like:
UEFI: SanDisk...✅ ← use this one- Avoid entries that just say
SanDisk...(Legacy BIOS mode)
✅ 3. Check Disk Visibility in Ubuntu Installer
From the Ubuntu “Try Ubuntu” desktop, open a terminal and run:
lsblk
or
sudo fdisk -l
You’re looking to see whether your internal SSD (e.g., /dev/nvme0n1 or /dev/sda) shows up.
If only /dev/sdb (your USB) appears, your internal drive isn’t detected — likely due to RAID mode or missing drivers.
✅ 4. Fix RAID → AHCI in Windows (if needed)
If your BIOS is set to RAID, you need to:
a. Boot into Windows 11
b. Press Win + R → type regedit → navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStorV
Set Start to 0.
Then also:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\iaStorAVC\StartOverride
Set 0 to 0.
And:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\storahci
Set Start to 0.
Reboot into BIOS → change SATA mode from RAID to AHCI.
Then boot into Windows — it will reconfigure itself, and after that, Ubuntu should see the drive.
✅ Summary:
| Step | Goal |
|---|---|
| BIOS: Disable Secure Boot, enable UEFI, set SATA/NVMe to AHCI | So Ubuntu can detect the disk |
| Boot USB in UEFI mode | To properly detect the internal drive |
Run lsblk in live Ubuntu | Check if the drive is seen |
| Switch RAID to AHCI (via regedit) if needed | Allow Ubuntu to access NVMe SSD |