Asus EZ Mode: "no bootable device"

The BIOS could not find anything to boot from. Either the drive is genuinely missing, or it is there but the bootloader is broken. Here is how to tell which, and fix each.

Step 1 — confirm what the BIOS sees

From EZ Mode, look at the Storage Information panel on the right side of the screen. One of three things will be true:

Your SSD is listed with its model name and capacity → the drive hardware is fine. The bootloader is the problem. Skip to Step 3.
"Not Installed" or empty → the BIOS cannot see the drive at all. Go to Step 2.
A different drive is listed (e.g. a USB stick or a secondary SSD) → see Step 4.

Step 2 — when the BIOS does not see the drive

This is hardware territory. In order:

Power off, unplug, hold the power button for 30 seconds (residual charge drain).
Open the bottom panel. Reseat the M.2 SSD — pull it out and reinsert. For a 2.5" SATA SSD, reseat both ends of the cable.
Boot. Check Storage Information again.
Still missing? Try the SSD in another machine via a USB-to-NVMe enclosure (£8 on Amazon). If it works there, the laptop's M.2 slot has failed. If it does not work there either, the SSD has died.

Step 3 — when the drive is visible but no bootloader

This is the more common case. The fix: rebuild the boot configuration using Windows installation media.

On another working PC, download the Windows 10 or 11 Media Creation Tool from microsoft.com.
Plug in an empty USB stick (8GB+) and create a bootable Windows installer.
Plug it into the broken Asus. Power on, press F8 repeatedly at the Asus logo to open the boot menu. Pick the USB.
At the Windows installer screen, click Repair your computer → Troubleshoot → Startup Repair. Pick your Windows installation. Wait.
If Startup Repair fails, go back and pick Command Prompt instead. Run these in order:
```
bootrec /scanos
bootrec /rebuildbcd
bootrec /fixmbr
bootrec /fixboot
```
If bootrec /fixboot returns "Access Denied", run bcdboot C:\Windows /s C: /f UEFI instead (replace C: with whatever Windows shows your install drive as).
Reboot. If Windows still does not start, the EFI partition is missing entirely — see Step 5.

Step 4 — when the BIOS is trying to boot the wrong drive

F7 to switch to Advanced Mode → Boot → Boot Option Priorities. Drag Windows Boot Manager (your SSD) to position #1. Remove or deprioritise the USB / external drive. F10 to save.

Step 5 — recreating a missing EFI partition

This is the nuclear option but works when nothing else does. From the Windows installer's Command Prompt:

diskpart
list disk
select disk 0    (or whichever number is your SSD)
list partition

If you see no EFI partition (typically 100MB FAT32), create one:

create partition efi size=100
format quick fs=fat32 label=System
assign letter=S
exit
bcdboot C:\Windows /s S: /f UEFI

(C: assumes Windows is on partition C:; check with list volume first.)

Reboot. If this works, Windows starts normally and the partition stays. If it does not, the Windows installation itself is corrupted and a clean install is the realistic next step.

Why this normally happens

Most "no bootable device" cases I see come from one of three things:

A failed Windows update that left the bootloader in a broken state.
Disk cloning gone wrong — someone migrated to a new SSD with a clone tool that did not properly recreate the EFI partition.
Drive failure — common on cheap NVMe SSDs from 2018-2021. They tend to fail at the controller level around the 4-year mark, with the drive intermittently disappearing from the BIOS.

Frequently asked

My BIOS shows the SSD in Storage Information but says "no bootable device" — how is that possible? +

The BIOS sees the drive hardware (good) but cannot find a valid bootloader on it (the actual problem). This usually means the EFI System Partition is corrupted, the Windows Boot Manager entry was deleted, or Secure Boot is rejecting an unsigned bootloader. Run Startup Repair from Windows installation media — it fixes this in most cases.

I just installed a new SSD and got "no bootable device" — what now? +

A blank SSD has nothing to boot. You need to install Windows on it from a USB installer. The BIOS message just means "I looked, there is no operating system here" — which is correct for a fresh drive.

Could a CMOS battery cause "no bootable device"? +

Indirectly, yes. When the CMOS battery dies, BIOS settings reset to factory defaults at every boot — including the boot order, which loses the entry pointing at your SSD. Replace the CMOS battery (CR2032, around £2) and the boot order should stick.