Windows Says “Operating System Not Found”? Try These Fixes

Seeing the “Operating System Not Found” error when you turn on your computer? Instead of loading Windows, your PC stops at a black screen with a message such as “Operating System Not Found,” “Missing Operating System,” or “No Bootable Device.”

In most cases, this error means your computer can’t find the files it needs to start the operating system. This can happen due to an incorrect boot order, corrupted boot files, a disconnected or failing SSD/HDD, or changes to BIOS/UEFI settings. In this guide, we’ll explain what causes the Operating System Not Found error and walk you through proven solutions from simple checks like verifying the boot order to repairing Windows boot files and checking for hardware problems.

What Does “Operating System Not Found” Mean?

The “Operating System Not Found” error means your computer’s firmware (BIOS or UEFI) cannot locate a bootable operating system on your storage drive. During startup, your PC looks for the Windows boot files required to launch the operating system. If those files are missing, corrupted, or located on a drive that isn’t being detected, the startup process stops and displays this error. Depending on your computer’s manufacturer, you may see slightly different messages, including:

• Operating System Not Found
• Missing Operating System
• No Bootable Device
• No Boot Device Found
• Boot Device Not Found
• Reboot and Select Proper Boot Device

Although the wording differs, these messages all point to the same problem: your computer cannot find a valid Windows installation to boot from. Well, the error can occur for several reasons, including:

• Incorrect boot order – Your computer is trying to boot from the wrong device instead of your Windows drive.
• SSD or hard drive not detected – The storage drive may be disconnected, faulty, or not recognized by the BIOS/UEFI.
• Corrupted boot files – Important Windows boot files or the Boot Configuration Data (BCD) may be damaged.
• BIOS or UEFI settings changed – A BIOS reset or incorrect boot mode can prevent Windows from loading.
• Problems after installing or cloning an SSD – The new drive may not be properly configured as a boot device.
• Failing hard drive or SSD – Hardware failure can make the operating system inaccessible.

Before You Start

Before trying the fixes below, perform these quick checks. They only take a few minutes and may resolve the problem without any advanced troubleshooting.

• Remove any USB flash drives, external hard drives, memory cards, or DVDs connected to your computer.
• If you’ve recently installed a new SSD, hard drive, or other hardware, make sure it’s properly connected.
• Restart your computer once to rule out a temporary startup glitch.
• If possible, note when the error first appeared (for example, after a Windows update, a BIOS change, a power outage, or an SSD upgrade). This can help identify the cause more quickly.

Once you’ve completed these checks, follow the solutions below in order.

Fix 1: Check the Boot Order in BIOS/UEFI

An incorrect boot order is one of the most common causes of the “Operating System Not Found” error. If your computer is trying to boot from the wrong drive, it won’t be able to find Windows.

1. Restart your computer.
2. As soon as it starts, repeatedly press the BIOS/UEFI key. Depending on your computer, this is usually F2, Delete, F10, or Esc.
3. Open the Boot or Boot Priority menu.
4. Make sure your Windows SSD or hard drive is listed as the first boot device.
5. Save the changes and exit the BIOS/UEFI (usually by pressing F10).

Your computer will restart automatically. If the boot order was incorrect, Windows should now start normally.

Note: If your Windows drive doesn’t appear in the boot device list or storage information, turn off your PC and check its physical connection. For desktop computers, ensure the SATA data and power cables are securely connected. If you’re using an NVMe SSD, make sure it is properly seated in the M.2 slot. If the drive still isn’t detected after reconnecting it, the storage device may have failed and require replacement.

Fix 2: Run Windows Startup Repair

If the boot order is correct but Windows still won’t start, try Startup Repair. This built-in recovery tool can automatically detect and fix common startup problems, including damaged boot files and configuration issues.

How to run Startup Repair

• Boot your computer into the Windows Recovery Environment (WinRE).
  • If your PC fails to start several times, Windows may open WinRE automatically.
  • If not, start your computer using a Windows installation USB drive and select “Repair your computer”.

• Go to: Troubleshoot → Advanced options → Startup Repair

• Select your Windows installation if prompted.
• Wait while Windows scans for startup problems and attempts to repair them automatically.

• When the repair is complete, restart your computer and check if Windows boots normally.

Note: Startup Repair may take several minutes to complete. Avoid turning off your computer while the repair is in progress.

If Startup Repair couldn’t fix the problem or reports that it couldn’t repair your PC, continue to the next solution.

Fix 3: Rebuild the Boot Configuration Data (BCD)

If Startup Repair doesn’t resolve the problem, the Boot Configuration Data (BCD) may be corrupted or missing. Rebuilding the BCD can restore the boot information Windows needs to start properly.

How to rebuild the BCD

1. Boot into the Windows Recovery Environment (WinRE).
2. Select:Troubleshoot → Advanced options → Command Prompt
3. In the Command Prompt window, run the following commands one at a time, pressing Enter after each one:

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

4. If Windows installation is found, type Y and press Enter to add it to the boot list.
5. Close the Command Prompt and restart your computer.

If Windows starts normally, the problem was caused by corrupted boot configuration data.

Note: On some UEFI-based systems, the bootrec /fixboot command may display an “Access is denied” error. Since this command is not required in many cases, you can skip it.

If the error still appears after rebuilding the BCD, continue to the next fix to repair the EFI boot files.

Fix 4: Repair the EFI Bootloader (UEFI Systems)

If your computer uses UEFI instead of the older Legacy BIOS, the EFI boot files may be missing or damaged. Repairing the EFI bootloader can restore the files Windows needs to start.

Note: This fix only applies to computers using UEFI with a GPT disk. If you’re unsure, you can still try this method.

How to repair the EFI bootloader

• Boot into the Windows Recovery Environment (WinRE).
• Select:Troubleshoot → Advanced options → Command Prompt

• Type the following commands, pressing Enter after each one:

diskpart
list vol

• Identify the EFI System Partition, which is usually a small FAT32 partition (around 100–300 MB).
• Assign a drive letter to the EFI partition (replace X with the volume number):

select volume X
assign letter=S
exit

• Rebuild the EFI boot files by running:

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

• When you see “Boot files successfully created”, close Command Prompt and restart your computer.

If Windows still doesn’t start, continue to the next solution to check your drive for file system errors.

Fix 5: Check Your Drive for Disk Errors Using CHKDSK

File system errors or bad sectors on your SSD or hard drive can prevent Windows from locating the files it needs to start. Running the CHKDSK tool scans the drive for errors and attempts to repair them.

How to run CHKDSK

1. Boot into the Windows Recovery Environment (WinRE).
2. Select: Troubleshoot → Advanced options → Command Prompt
3. Type the following command and press Enter:

chkdsk C: /f /r

Note: If your Windows installation is on a different drive letter in WinRE, replace C: with the correct drive letter.

4. Wait for the scan to finish. This may take some time, especially on large drives.
5. When the scan is complete, restart your computer and check if Windows boots normally.

Fix 6: Repair Corrupted Windows System Files Using SFC

If important Windows system files are damaged or missing, your computer may fail to boot properly. The System File Checker (SFC) tool can scan for corrupted system files and replace them with healthy copies.

How to run SFC from WinRE

1. Boot into the Windows Recovery Environment (WinRE).
2. Select: Troubleshoot → Advanced options → Command Prompt
3. First, identify the drive letter where Windows is installed. In WinRE, it may not be C:.
4. Run the following command, replacing C: if your Windows installation uses a different drive letter:

sfc /scannow /offbootdir=C:\ /offwindir=C:\Windows

5. Wait for the scan to complete. If SFC finds corrupted system files, it will attempt to repair them automatically.
6. Restart your computer and check whether Windows starts normally.

Tip: If you’re unsure of your Windows drive letter in WinRE, use the diskpart and list volume commands to identify it before running SFC.

If the “Operating System Not Found” error still appears, continue to the next solution to reset your BIOS/UEFI settings.

Fix 7: Reset BIOS/UEFI Settings to Default

If the error started after changing BIOS/UEFI settings or updating the BIOS, resetting the firmware to its default settings may restore the correct boot configuration.

How to reset BIOS/UEFI settings

1. Restart your computer and enter the BIOS/UEFI setup by pressing F2, Delete, F10, or Esc during startup.
2. Look for an option such as Load Setup Defaults, Load Optimized Defaults, or Restore Defaults.
3. Select the option and confirm the reset.
4. Save the changes and exit the BIOS/UEFI (usually by pressing F10).
5. Restart your computer.

After the reset, verify that your Windows SSD or hard drive is still selected as the primary boot device. If Windows still doesn’t start, continue to the next fix.

Note: Resetting the BIOS/UEFI only restores firmware settings. It does not delete Windows, your files, or installed programs.

Fix 8: Check the Health of Your SSD or Hard Drive

If none of the previous solutions work, your SSD or hard drive may be developing a hardware problem. A failing drive can prevent your computer from reading the Windows boot files, resulting in the “Operating System Not Found” error.

Signs your storage drive may be failing

• The drive is not always detected by the BIOS/UEFI.
• You hear unusual clicking or grinding noises (hard drives only).
• Your computer frequently freezes or crashes.
• Windows was extremely slow before the error appeared.
• You recently received disk or SMART warnings.

What you can do

• If the drive is detected, connect it to another computer and back up your important files as soon as possible.
• Use your SSD or hard drive manufacturer’s diagnostic tool to check the drive’s health.
• If the diagnostic test reports hardware failure, replace the drive and reinstall Windows or restore your data from a backup.

If the drive passes the health check but Windows still won’t boot, your final option is to reinstall Windows.

Fix 9: Reinstall Windows

If you’ve tried all the previous solutions and still see the “Operating System Not Found” error, reinstalling Windows may be the only remaining option. This replaces damaged system files and creates a new boot configuration.

Important: Reinstalling Windows may remove your apps and personal files if you choose a clean installation. If your storage drive is still accessible, back up your important data before continuing.

How to reinstall Windows

1. Create a Windows installation USB using another working computer.
2. Insert the USB drive into the affected computer and boot from it.
3. On the Windows Setup screen, select your language and keyboard layout, then click Next.
4. Click Install now and follow the on-screen instructions.
5. Choose the installation option that best suits your needs:
   • Upgrade (if available): Attempts to keep your files and apps.
   • Custom: Performs a clean installation of Windows.

After Windows is installed, reinstall your drivers, restore your files from a backup, and install any available Windows updates.

If the error persists even after a clean installation, the problem is likely caused by a failing SSD, hard drive, motherboard, or another hardware component that requires further diagnosis or replacement.

How to Prevent the “Operating System Not Found” Error

While this error isn’t always avoidable, following a few best practices can reduce the chances of it happening again:

• Keep regular backups: Back up your important files to an external drive or cloud storage so you can recover them if your PC won’t boot.
• Shut down your PC properly: Avoid forcing your computer to power off, as unexpected shutdowns can corrupt boot files.
• Be careful when changing BIOS/UEFI settings: Only modify boot settings if you understand their purpose.
• Check your SSD or hard drive health regularly: Use the manufacturer’s diagnostic tool to detect potential drive issues before they lead to failure.
• Don’t interrupt Windows updates: Let updates finish completely, especially those involving system or boot files.
• Use a reliable power source: A UPS (Uninterruptible Power Supply) can help protect your computer from sudden power outages during startup or updates.

Following these simple practices can help keep your Windows installation healthy and reduce the risk of future startup problems.

Frequently Asked Questions (FAQs)