Fix "Reboot and Select Proper Boot Device" on Windows 10/11

The fast answer. "Reboot and select proper boot device" is a firmware message — the BIOS/UEFI couldn't find anything bootable. The most common cause is a wrong boot order. Enter BIOS (usually Del or F2 at power-on), go to the Boot tab, and move your Windows SSD or HDD to position 1. If the drive doesn't appear in the boot list at all, the cable is loose or the drive has failed — fix the hardware before running any commands. If the drive is listed but the error persists, the boot records are corrupt; open a Command Prompt in WinRE and run:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

Why this happens

Wrong boot order — the firmware is trying to boot a USB drive, DVD, or secondary disk ahead of the Windows drive. This is the most common cause and happens after CMOS resets, BIOS updates, or adding new hardware.
Loose or unseated drive connection — a SATA data or power cable worked loose, or an M.2 drive isn't properly screwed down. The firmware sees no drive.
UEFI/Legacy (CSM) mode mismatch — Windows 10/11 installed in UEFI mode on a GPT disk won't boot if Legacy/CSM mode is active, and vice versa. A CMOS reset or board replacement often flips this setting.
Boot partition not marked active — on MBR/Legacy-partitioned disks, the system partition must carry the active flag. Partition tools or disk changes can clear it.
Corrupted MBR, BCD, or boot sector — power loss during a write, malware, or a failed Windows Update damaged the boot records the firmware hands control to.

Step-by-step fix

Step 1 — Fix the boot order in BIOS/UEFI

Restart and enter BIOS setup (usually Del, F2, or Esc — watch the splash screen). Go to the Boot tab or Boot Priority section. Move your Windows SSD or HDD to position 1. Remove any USB drives or DVDs from the boot priority list. Save with F10 and reboot. Many systems also support a one-time boot menu with F12, which lets you pick the boot device without changing the stored BIOS order.

Step 2 — Verify the drive is detected; reseat cables

While in BIOS, locate the drive list (look for SATA Configuration or NVMe Configuration). If your drive is missing, power off and reseat: for SATA drives, firmly reseat both ends of the data cable and the power connector, and try a different SATA port; for M.2 drives, remove the retaining screw, re-slot the drive, and tighten the screw. If the drive still doesn't appear in BIOS, it has failed — software repairs won't help at that point.

Step 3 — Match UEFI/Legacy mode to your disk

In BIOS, look for Boot Mode, CSM (Compatibility Support Module), or a UEFI/Legacy toggle. Windows 10/11 on a GPT disk needs UEFI mode with CSM disabled. Older installs on MBR disks use Legacy/CSM mode. A CMOS reset often reverts this to a firmware default that doesn't match your Windows install. Restore the setting to what the OS was installed with and reboot. Do not enable CSM on a UEFI/GPT system — it immediately makes a working Windows install invisible to the boot manager.

Step 4 — Rebuild boot records from WinRE

This error appears before Windows starts loading, so forcing three failed boots usually cannot trigger Automatic Repair. Instead, boot a Windows 10/11 install USB and choose Repair your computer → Troubleshoot → Advanced options → Command Prompt. Run these in order:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

When bootrec /rebuildbcd finds a Windows installation, type Y to add it. Reboot and test.

UEFI/GPT note: on modern UEFI systems bootrec /fixboot returns "Access is denied" — this is expected and not the real fix on those machines. Continue to Steps 5 and 6.

Step 5 — Mark the system partition active (MBR/Legacy disks only)

On MBR-partitioned disks, the system partition must be marked active. In the WinRE Command Prompt, run:

diskpart
list disk
select disk 0
list partition
select partition 1
active
exit

Replace 1 with the number of the system partition — typically the small partition (100–500 MB) at the start of the disk. After marking it active, rerun bootrec /fixmbr and bootrec /fixboot, then reboot.

Step 6 — Rebuild EFI boot files (UEFI/GPT disks only)

If Steps 4–5 didn't resolve the error on a UEFI/GPT system, the EFI boot files need to be rebuilt. In WinRE Command Prompt, assign a letter to the EFI System Partition:

diskpart
list vol
select vol 1
assign letter=S
exit

The EFI partition is the small (~100 MB) FAT32 volume — confirm the volume number with list vol first. Then rebuild the boot files:

bcdboot C:\Windows /s S: /f UEFI

Reboot and test. See the 0xc000000e boot error page for the full UEFI walkthrough including how to verify the EFI partition is intact.

Data safety: Correcting the boot order and running bootrec don't touch your data files. However, a drive that still shows this error after a connection check may be in early failure. If the files on this machine matter and you don't have a backup, image the drive before running repairs. A dying drive can lose data under the stress of chkdsk /r. Never run repairs on the only copy of irreplaceable data.

GRAM tip: Once the machine boots again, plug in GRAM — a free portable repair toolkit that runs from a USB inside Windows — to check the drive's SMART health (reallocated and pending sectors tell you whether the drive that threw this error is at risk), read the event logs, and let its AI agent confirm whether the real cause was the boot order, a cable, a firmware setting, or early-stage drive failure so the error doesn't come back.

Download GRAM free See AI pricing →

FAQ

Can I fix this without a second working computer?

Correcting the boot order only requires BIOS access — no extra media needed. For the bootrec and bcdboot repairs in Steps 4–6, you'll need a Windows 10/11 install USB. Unlike blue-screen errors, "Reboot and select proper boot device" appears before Windows starts loading, so forcing three failed boots usually can't trigger Automatic Repair. WinRE won't open on its own. Creating a Windows install USB does require a second working PC. (GRAM runs inside Windows rather than from boot media — use it once the machine boots again to verify disk health and confirm the root cause.)

My drive doesn't appear in BIOS at all. Is it dead?

Not automatically. Reseat the cable at both ends first (SATA drives), or re-slot and tighten the retaining screw (M.2 drives). Try a different SATA port and a different data cable — SATA cables fail more often than people expect. If the drive appears in BIOS after reseating, you've found the problem. If it still doesn't show up, or shows up only intermittently, the drive is likely failing. At that point, prioritize data recovery over any software repair attempt.

Will bootrec or marking a partition active erase my files?

No. bootrec /fixmbr and bootrec /fixboot rewrite only the master boot record and boot sector — not your data. Marking a partition active sets a flag in the partition table; it does not wipe or reformat the partition. Your files remain intact. The only risk is running chkdsk /r on a drive that's already failing, because the sector scan stresses weak areas. Image the drive first if the data matters.

I changed BIOS settings and the error got worse. How do I undo?

In BIOS/UEFI setup, find Load Setup Defaults, Reset to Default, or Optimized Defaults in the Exit menu. Loading defaults restores all firmware settings to factory state, clearing any accidental changes including mode switches. After loading defaults, re-apply only the boot order change and save. If the machine still doesn't boot, work through Step 3 (UEFI/Legacy mode) using the defaults as your starting point.