Missing Operating System or Operating System Not Found | 10+ Fixes

The missing operating system error message implies that your computer has a boot problem that the computer was unable to find the operating system to to boot up. Follow to learn the causes and get the fixes for 'missing operating system' or 'operating system not found' error for Windows 11/10/8/7/XP/Vista immediately.

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• Solution 1. Disconnect External Devices
• Solution 2. Check If the Hard Drive Is Detected by BIOS
• Solution 3. Run Startup Repair or System Restore + Repair MBR
• Solution 4. Rebuild MBR without Windows Installation CD/DVD
• Solution 5. Test Hard Drive Problems
• Solution 6. Set BIOS to Default Settings
• Solution 7. Check Boot Order
• Solution 8. Repair MBR with the Installation CD/DVD
• Solution 9. Repair MBR for HP
• Solution 10. Set the Correct Partition Active

The "missing operating system" or "operating system not found" error message usually appears on a black window when you start Windows computers. It would prevent you from booting Windows. This error is very common for Dell, Acer, Lenovo, HP, and Sony desktops and laptops. You can read on to get error details or skip directly to solutions.

To fix this, first, remove all external media like USB drives and DVDs, then check and correct the boot order in the BIOS to ensure the hard drive is the first boot device. If the problem persists, you may need to repair the boot files using a Windows installation USB or attempt to reset the BIOS to default settings. Read the following content to learn more fixes, and feel free to share this post.

Why Is My Computer Saying No Operating System Found?

So what does missing operating system mean? A "missing operating system" error means the computer's BIOS can't find the necessary files to start Windows, which can be caused by a corrupted operating system, a damaged hard drive, or incorrect boot order settings. Generally, when something goes wrong with the BIOS configuration, hard drive health, or the Master Boot Record (MBR), you can't boot Windows and will get this error.

This error usually appears when the computer can't locate a valid Windows installation to boot from. The most common reasons include:

System Drive Not Detected in BIOS/UEFI

• The BIOS can't find the hard drive or SSD where Windows is installed, often due to a loose cable, faulty connection, or disabled drive.

Hard Drive or SSD Failure

• Physical damage, bad sectors, or NAND wear may prevent the disk from reading the system partition properly.

Incorrect BIOS/UEFI Settings

• Wrong boot order, disabled system disk, or switching between Legacy and UEFI modes can cause startup failure.

Corrupted Boot Records (MBR or BCD)

• Power loss, malware, or improper cloning can damage Windows’ boot files, leading to a missing OS message.

Wrong or Inactive System Partition

• On legacy BIOS systems, if the wrong partition is set as active, Windows won’t load.

External Devices Interfering with Boot

• USB drives, SD cards, or external HDDs may override the system disk in boot priority.

Corrupted Partition Table or System Files

• Damaged GPT/MBR structures or deleted bootloader files can make the OS unrecognizable.

Cloning or Migration Errors

• After moving Windows to a new SSD/HDD, missing EFI or recovery partitions can trigger boot issues.

Note: If the BIOS fails to detect the operating system, you will receive one of the following error messages, which tells the same problem on different operating system versions.

Error message 1: Missing Operating System

Error message 2: Operating system not found

So how could you get rid of this error, making computer detect the operating system and boot up successfully again? Here is what's we intent to help in the next part. Continue reading and you'll get fixes to fix operating system not found error instantly.

How to Fix Missing Operating System or Operating System Not Found Error

After knowing the causes for an operating system not found or missing in Windows, now it's time to apply effective solutions to restore the missing operating system. Don't forget to share this article to let others know about the causes behind this issue.

Solution 1. Disconnect External Devices

In many cases, external drives or USB devices can interfere with your PC's boot sequence. Windows may mistakenly attempt to boot from these devices instead of the system drive, triggering the "Operating System Not Found" message.

• Power off your computer completely.
• Unplug all unnecessary external devices, including USB drives, external SSD/HDD, memory cards, docking stations, and printers.
• Restart your computer with only essential hardware connected.
• If Windows boots normally, reconnect your devices one by one to identify the culprit.
• Keep the problematic device unplugged during startup or change the boot priority if needed.

Read "Can a bad external hard drive stop PC from booting?" from Reddit.

Solution 2. Check If the Hard Drive Is Detected by BIOS

When non system disk or disk error occurs on the computer, BIOS settings won't be able to detect and load the operating system, then your computer won't be able to boot up. In case of this, you may first check the BIOS settings and see if the OS hard drive is set as the Boot drive. Here are the detailed steps you can follow:

Step 1: Press and hold "F12/F10" while pressing the "Power" button to turn on the PC.

Step 2: Release F12/F10 when the BIOS Setup Utility is displayed.

Step 3: Try to find IDE Primary Master, IDE Primary Slave, IDE Secondary Master, and check whether they can be detected or not.

For more fixes, you can refer to this page to fix hard disk not detected in bios error with success. 

If no disk is shown or displayed as None/Not Detected, it means that the BIOS doesn't detect the drive and you may select None to Auto. This may solve the Operating System not found error.

If the system disk information is displayed, it means that BIOS can detect the hard drive and you need exit BIOS.

Solution 3. Run Startup Repair or System Restore + Repair MBR (via WinPE or Installation Media)

Windows provides built-in recovery tools that can automatically fix boot issues. If those fail, you can manually rebuild the boot configuration from Command Prompt using system repair commands.

Step 1. Create or insert a Windows installation USB or recovery drive. (Click here to learn how to create a Windows repair USB.)

Step 2. Boot your computer from the USB drive by selecting it in the BIOS/UEFI boot menu.

Step 3. Once in the Windows setup screen, select Repair your computer > Troubleshoot > Advanced Options.

• Try Startup Repair first > Windows will scan and fix missing or corrupted boot files automatically.

If Startup Repair fails, open Command Prompt and type the following commands:

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

Restart your PC and check if Windows boots properly.

If not, try System Restore from the same "Advanced Options" menu to revert your system to an earlier working state.

Notes:

Before using bootrec commands, it's recommended to back up your important data, as improper use can make partitions inaccessible.

If your disk uses GPT/UEFI, replace MBR commands with:

• bcdboot C:\Windows /s S: /f UEFI

Some OEMs (e.g., Dell, HP) offer proprietary recovery tools you can try if Windows repair fails.

Microsoft also warns that repairing MBR on a virus-infected or failing drive can cause permanent boot record damage.

Solution 4. Rebuild MBR without Windows Installation CD/DVD

If you prefer an easier and safer way to rebuild or repair the MBR disk, you may apply third-party partition magic software - EaseUS Partition Master to perform an automatic repair. 

Boot your Windows from the WinPE environment you created and start to repair MBR with a few clicks.

Step 1. Create a WinPE bootable disk

• Launch EaseUS Partition Master, and click "Bootable Media" on the toolbar. Select "Create bootable media".
• Click "Next" to finish the process.

Step 2. Boot EaseUS Partition Master Bootable USB

• Connect the bootable USB or CD/DVD to your PC. 
• Press F2 or Del when you restart the computer to enter the BIOS screen. Set and boot your computer from "Removable Devices" or "CD-ROM Drive". And then EaseUS Partition Master will run automatically.

Step 3. Rebuild MBR

• Click "Toolkit" and choose "Rebuild MBR".

• Select the disk and the type of MBR. Then, click "Rebuild".

• After that, you can see "MBR has been successfully rebuilt on Disk X".

Solution 5. Test Hard Drive Problems

The next move is to detect if the OS hard drive contains any problems or errors in BIOS settings. Follow the steps here and learn how to do so on your own:

Step 1: Press and hold "F10" and press the "Power" button to turn on the PC > Release F10 after the PC screen display you with a test.

Step 2: Use the right arrow to select the "Tools" menu in the BIOS Setup Utility.

Step 3: Then select "Hard Drive Self Test" > Press "Enter" to start the test.

After the test, you'll get two results:

#1. All Tests Passed

This means the hard drive is not damaged. You may jump to Solution 3 to reset BIOS to the default state so as to getting rid of missing operating system issue.

#2. The Test Failed

You should contact your hard disk or computer manufacturer for a replacement as long as these devices are under warranty.

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Solution 6. Set BIOS to default settings

Improper settings or incorrect BIOS settings may also cause the issue 'operating system not found' in your PC. You can try to set BIOS to default settings to solve the problem.

Step 1: Restart PC and enter BIOS.

Step 2: Find BIOS and enable the default setup option, including Load Optimal Defaults, Get Default Values, Load Optimized Defaults, Load Setup Defaults, and so on.

Step 3: Press "F10" to save changes and quit from BIOS.

If this method doesn't work, the MBR disk could be damaged and you may jump to Solution 4 to fix MBR Windows10 or newer operating system with preofssional MBR repair method.

Further Reading: Windows 11 Black Screen with Cursor

Solution 7. Check Boot Order

An incorrect boot order is one of the most common causes of the "Operating System Not Found" message. Your computer may be trying to boot from the wrong disk or an empty USB device.

Step 1. Restart your computer and press the appropriate key (usually F2, F10, Del, or Esc) to enter the BIOS/UEFI setup.

Step 2. Go to the Boot or Boot Order tab.

Step 3. Make sure the drive containing your Windows installation (often labeled Windows Boot Manager or your SSD model) is listed first.

Step 4. Move USB drives, DVD drives, or Network Boot options below your system disk or disable them.

Solution 8. Repair MBR with the Installation CD/DVD

Both wrong operation and virus infection can damage MBR, which locates in the first sector - usually sector 0 of the hard disk. Thus, Windows will not boot. You can try to repair MBR using the Windows installation disk in Command Prompt.

Insert Windows Operating System Disc to the optical (CD/DVD) drive

Step 1: Press the "Power" button to turn on the PC > Hit "Enter" when Boot from CD prompt.

Step 2: Press "R" key in Windows Setup Menu to start the Recovery Console.

Step 3: Type: FIXMBR at the C:\> prompt and hit "Enter".

Step 4: Press "Y" key > hit "Enter" when asked if you want to write a new MBR.

Step 5:  Restart PC by pressing the "Power" button when the MBR completes the writing process.

Solution 9. Repair MBR for HP

Some brands provide customers with inbuilt tools to deal with MBR issues. For example, the Windows Operating System Disc (OSD) provided with HP notebook PC can be used to repair the Master Boot Record.

Follow all steps at: https://support.hp.com/us-en/document/c00476274

Solution 10. Set the Correct Partition Active

When Windows is running under Legacy BIOS + MBR mode, the boot partition/system partition should be set as active so that MBR can pass boot right to the boot manager and find Windows. If the system partition or boot partition is not set to active, you may encounter the operating system not found issue.

In the same partition tool, create the EaseUS Partition Master Bootable USB first, and follow the steps to set the boot partition active:

Step 1. Run EaseUS partition manager software. On the disk map, right-click the target partition and choose "Advanced".

Step 2. Then, select "Set Active" from the drop-down menu. Click "Yes".  And choose "Execute 1 Task(s)" and click "Apply".

Conclusion

All effective solutions to the "Missing Operating System" or "Operating system not found" error are carefully presented on this page. You may try any one of the methods to resolve the issue and get a healthy Windows system back, and continue using your computer again.

As long as you are setting a healthy hard drive as the boot drive, which could be detected by the BIOS settings, the computer will be able to find and load your OS from the boot drive successfully. When an issue occurs with a malfunctioning MBR table or the OS partition is not set as active, you may turn to EaseUS Partition Master for help.

FAQs About Missing Operating Systems or Operating System Not Found

If you still have doubts about this issue, relax and follow the quick answers to each question as listed below.

1. Why is my PC showing missig operating systems?

The causes of missing operating system on Windows computer could be diverse, including OS drive not detected by BIOS, incorrect BIOS settings, MBR corruption, OS drive is not set as active, etc.

2. What does missing operating system mean?

A "missing operating system" error means a computer cannot find the necessary software to start up, preventing it from booting into Windows. This can be caused by a misconfigured BIOS/UEFI, a corrupted or damaged hard drive, a deleted or corrupted bootloader file, or an inactive system partition.

3. How do I fix a missing operating system Windows 10/7?

According to the solutions provided by this page, you can successfully get rid of missing operating system error on Windows 10 or Windows 7 computers by trying to modifying BIOS settings to its default settings, repairing corrupted MBR partition table, and set OS drive as active, etc. For more details, revert to the repsective solutions on this page for help.