How to fix a computer that says no boot device found and get it running again

The "no boot device found" error means your computer can’t find the drive containing its operating system, so it can’t start up. This can happen if the drive is disconnected, the BIOS or UEFI isn’t set to boot from it, or the boot files are damaged. You can fix it by checking hardware connections, adjusting BIOS settings, repairing the bootloader or operating system, and testing or replacing the drive if needed.

What does 'no boot device found' actually mean?

The message "no boot device found" appears when your computer tries to start but can’t locate the storage device that holds the operating system. This device is usually a hard drive or SSD with Windows, macOS, or Linux installed. Without finding the boot device, the system can’t load the software needed to run.

Common causes include hardware problems like a disconnected or failing drive, BIOS or UEFI settings that no longer point to the correct drive, or corrupted boot files that block startup. Sometimes a recent update or system change resets settings or damages files, triggering this error.

Exact error messages vary by system but typically say something like:

No boot device found
No bootable device -- insert boot disk and press any key
Operating system not found

Before you start

This guide applies to desktop and laptop computers running Windows, macOS, or Linux.

You’ll need access to your computer’s BIOS or UEFI firmware settings and, for some steps, administrator privileges.

Before making changes:

• Make sure the computer is fully powered off and unplugged before opening it.
• If possible, have another working computer to create recovery media.
• Backup any accessible important data if you can access the drive through recovery options or by connecting it to another computer.

Restarting the computer can sometimes clear temporary issues but if the error repeats, proceed with the troubleshooting steps.

Could it be a loose or disconnected drive cable?

A common cause is a loose or disconnected cable between your hard drive or SSD and the motherboard.

For desktop computers, check the connections safely:

1. Turn off your computer and unplug it from the power source.
2. Open the side panel to access the inside.
3. Find the hard drive or SSD. It looks like a rectangular box connected by two cables: the power cable and the data (SATA) cable.
4. Gently press on both ends of each cable—where they connect to the drive and to the motherboard or power supply—to make sure they’re secure.
5. Close the case, plug the computer back in, and turn it on.

For laptops, opening the case is more delicate and varies by model. Only attempt if you have clear instructions from the manufacturer and feel confident. Otherwise, skip this step or seek professional help to avoid damage or voiding warranty.

How to check and adjust boot order in BIOS or UEFI

The BIOS or UEFI firmware controls which device the computer tries to start from first. If the boot order doesn’t prioritize your main hard drive or SSD, the computer may report "no boot device found."

To check and fix boot order:

1. Restart your computer.
2. Immediately press the key to enter BIOS/UEFI setup. Common keys are Delete, F2, Esc, or F10; the correct key usually appears briefly on the screen during startup.
3. Once inside BIOS/UEFI, locate the "Boot" or "Boot Order" menu. The exact location depends on your computer manufacturer.
4. Look for your hard drive or SSD in the list of boot devices. If it’s not first, move it to the top of the boot priority.

Boot > Boot Priority > Move your main drive to the top

5. Save your changes and exit BIOS/UEFI (usually by pressing F10).

If your drive doesn’t appear at all in the boot device list, this may indicate a hardware connection problem or a failing drive.

How to repair the bootloader or operating system

If hardware and BIOS settings are correct, corrupted boot files might be causing the problem.

For Windows:

1. Create a Windows installation USB or DVD using Microsoft’s Media Creation Tool on another working computer, if you don’t have one.
2. Boot your computer from the USB/DVD by selecting it in the boot menu.
3. Choose "Repair your computer" instead of "Install."
4. Navigate to "Troubleshoot" > "Advanced options" > "Startup Repair." Let Windows attempt to fix boot issues automatically.

If Startup Repair doesn’t resolve it, use the Command Prompt from the recovery options:

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

These commands repair the bootloader and rebuild boot configuration data.

For macOS:

1. Restart and hold Command + R to enter Recovery Mode.
2. Open Disk Utility and run "First Aid" to repair the disk.
3. If necessary, reinstall macOS from the recovery options.

These steps repair damaged system files or bootloaders that prevent startup.

How to test your hard drive or SSD for failure

If repairs don’t work, the drive might be failing.

Signs of hardware failure include unusual noises from the drive, frequent crashes, or the BIOS not detecting the drive.

You can test the drive using built-in tools or third-party software:

• On Windows, run:

chkdsk C: /f /r

• Use manufacturer tools like SeaTools for Seagate drives.

• For SSDs, programs like CrystalDiskInfo provide health status.

• On macOS, use Disk Utility’s "First Aid".

If tests find errors that can’t be fixed or the drive isn’t detected, replacement is necessary. If possible, back up important data before replacing the drive.

What to do if nothing else works

If you’ve tried all these steps and the error remains, take care before proceeding.

If you can access your files through recovery mode or by connecting the drive to another computer, back up important data immediately.

At this stage, it’s best to consult a professional technician. They can accurately diagnose hardware problems, recover data, or replace parts without risking further damage.

Avoid opening the computer further or attempting advanced repairs unless you have experience, as this can void warranties or cause more harm.

Conclusion

The "no boot device found" error usually means the computer can’t detect or access the drive with your operating system. Start by checking hardware connections and BIOS boot order. If those are correct, repair the bootloader or operating system files. If the drive is failing, test it and replace it if necessary. Always back up your data when possible and seek professional help if the problem persists or if you’re unsure about any step.