7 + Fixes: Missing Operating System or Operating System Not Found

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.

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Causes of Missing Operating System/Operating System Not Found

Generally, when something goes wrong with the BIOS configuration, hard drive health, or the Master Boot Record (MBR), you can't boot the Windows and will see the mentioned two error messages. To be specific, the causes that lead to Operating System Not Found are as follows.

• The basic input/output system (BIOS) does not detect the hard disk
• The hard disk drive is damaged
• Improper/incorrect BIOS settings
• Windows Master Boot Record (MBR) is corrupt/damaged
• An incompatible partition is set as active

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.

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7 Solutions to Fix Mising 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. 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 2. 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.

Solution 3. 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 4. 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 5. 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 6. Repair MBR for HP

Solution 4~5 to corrupted MBR repair is applicable to various computer/laptop brands. On top of that, 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 7. 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 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 your are setting an healthy hard drive as the boot drive which could be detected by the BIOS settings, the computer could be able to find and load your OS from the boot drive successfully. When it issue occurs to malfunctioning MBR table, or 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 is missing operating system Windows 10?

The missing operating system in Windows 10 error is a system error that occurs to most operating systems including Windows 10/11, and older Windows 8.1/8/7/Vista. With this error on a computer, you'll see that the computer cannot fully boot up from the OS drive. Instead, the computer will present you with a black screen with error messages like "Missing Operating System..." or "Operating System no found...". This error will linger if you can't find the correct fixes for it.

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.