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

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Workable SolutionsStep-by-step Troubleshooting
Fix 1. Kiểm tra BIOSPress & hold "F12/F10" khổng lồ enter BIOS...Full steps
Fix 2. Reboot from a bootable diskPress và hold "F10" & press "Power"...Full steps
Fix 3. Phối BIOS to default settingsFind BIOS & enable the default setup option...Full steps
Fix 4. Rebuild MBR using cmdInsert the Windows installation CD/DVD...Full steps
More FixesBoot PC from Partition Master ...Full steps

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 & will see the mentioned two error messages. Khổng lồ be specific, the causes that lead to lớn Operating System Not Found are as follows.

The basic input/output system (BIOS) does not detect the hard diskThe hard disk drive is damagedImproper/incorrect BIOS settingsWindows Master Boot Record (MBR) is corrupt/damagedAn incompatible partition is set as active

Note: If the BIOS fails to lớn 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


7 Solutions to Fix Operating System Not Found or Missing

After knowing the causes for an operating system not found or missing in Windows, now it"s time khổng lồ apply effective solutions to lớn restore the missing operating system.

Solution 1. Kiểm tra if the hard drive is detected by BIOS

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 thiết đặt 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.


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 OS 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. Chạy thử hard drive problems

Step 1: Press & hold "F10" and press the "Power" button khổng lồ 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" thực đơn in the BIOS thiết lập Utility.

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


After the test, you"ll get two results:

#1. All tests passed

the hard drive is not damaged. You may jump khổng lồ Solution 3 to reset BIOS khổng lồ the mặc định state.

#2. The kiểm tra failed

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

Solution 3. Set BIOS to mặc định settings

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

Step 1: Restart PC và enter BIOS.

Step 2: Find BIOS và enable the default cài đặt option, including Load Optimal Defaults, Get default Values, Load Optimized Defaults, Load thiết đặt Defaults, và so on.

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Step 3: Press "F10" khổng lồ save changes & quit from BIOS.


If this method doesn"t work, the MBR disk could be damaged và you may jump khổng lồ Solution 4 to find the MBR disk repair method.

Solution 4. Repair MBR with the installation CD/DVD

Both wrong operation & 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 lớn repair MBR using the Windows installation disk in Command Prompt.

Notice:Microsoft says the fixmbr command that used in this method may damage your partition table if a vi khuẩn presents or if a hardware problem exists. The existing partitions might be inaccessible so that data cannot be used. Partition Master can help rebuild MBR without bringing any damage to lớn data & partition since it operates the master boot record only. For detailed steps, go to Solution 5.

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

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

Step 2: Press "R" key in Windows setup Menu khổng lồ start the Recovery Console.

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

Step 4: Press "Y" key > hit "Enter" when asked if you want to lớn 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 & safer way to lớn rebuild or repair the MBR disk, you may apply third-party partition magic software - Partition Master to lớn 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 Partition Master, click "WinPE Creator" on the toolbar. Select to create the bootable disk on a USB drive. If your computer has a CD/DVD drive, you can also create the bootable disk lớn CD/DVD.Click "Proceed" to finish the process.

Step 2. Boot 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 và boot your computer from "Removable Devices" or "CD-ROM Drive". Và then Partition Master will run automatically.

Step 3. Rebuild MBR

Right-click the disk whose MBR is damaged. Choose "Rebuild MBR" to continue.Select the type of MBR with the current operating system. Then, click "OK".

Click the "Execute Operation" button at the top-left corner & click "Apply" to build the MBR. After that, your computer can boot normally again.

Solution 6. Repair MBR for HP

Solution 4~5 khổng lồ corrupted MBR repair is applicable khổng lồ various computer/laptop brands. On vị trí cao nhất 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 khổng lồ repair the Master Boot Record.

Follow all steps at

Solution 7. Phối the correct partition active

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

In the same partition tool, create the Partition Master bootable USB first, và follow the steps lớn set the boot partition active:

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

Step 2. Then, select "Set Active" from the drop-down menu. The software will automatically execute the operation và create an active partition for you.