User case: How to solve Operating System not found?
“Hello everyone, I reinstalled Windows 10 on a macro computer four days ago and it was running well. After saving some files to my computer today, its running speed slowed down, so I reset my computer in settings (deleting all content). During the reset process, I accidentally turned off my computer and when I reopened it, it prompted ‘Operating System not found’. I would like to know if anyone else has encountered this situation before. Also, how can I solve this problem? Thank you!”
Operating System not found
Why does the computer prompt “Operating System not found”?
Have you ever encountered errors like “Operating System not found” or “Miss Operating System” when using HP, Sony, Acer, and Lenovo computers? This type of error can prevent you from successfully starting Windows. Before attempting to fix this error, you should first understand the reason why the operating system was not found. The reasons for “Operating System not found” or “Miss Operating System” appearing in Windows 11/10/11 are:
The system hard drive is damaged.
The Basic Input/Output System (BIOS) did not detect the installation of Windows 11/10/11 hard drives/disks.
The Windows 11/10/11 boot file in the system partition is no longer active.
The MBR (Master Boot Record) of Windows 11/10 is corrupt.
Four methods to fix “Operating System not found” errors
How to solve the problem of Operating System not found? Based on the possible causes of errors, we have summarized four methods to help you fix issues where the operating system cannot be found in Windows 11, 10, 8, and 7.
Method 1. Check the hard drive
Firstly, you can test if there are any issues with the hard drive. To achieve this, you can take the following steps:
- Turn off the computer and wait for 5 seconds.
- Press the power button to start the computer, and repeatedly press the F10 button to enter BIOS settings.
BIOS settings
- Use the arrow keys to navigate to Diagnosis>Primary Hard Drive Self Test.
- Select Primary Hard Drive Self Test, then press Enter to start the test.
The hard drive self check will first execute a “Quick Test”, followed by a “Comprehensive Test”. During each testing period, the window will display a status bar and estimated completion time.
If all tests pass, the hard drive is not damaged.
If the test fails, as long as these devices are within the warranty period, you can contact your hard drive or computer manufacturer for replacement.
Method 2. Activate Windows partition
When the system partition with Windows installed is disabled, there may also be issues with “Operating System not found” or “Miss Operating System” on Windows 11/10. In this case, you can fix it by reactivating the Windows partition.
- Open your computer and start it from the Windows installation media. In the “Install Now” screen, click “Repair Computer”.
Repair computer
- Click on “Troubleshooting”>”Advanced Options”>”Command Prompt”.
command prompt
- In the command prompt window, enter the following command and press enter after each command:
Diskpart
List disk: will display a list of all disks connected to your computer, search for the system disk.
Select disk [number]: Replace [number] with the system disk number.
List volume: It will display all partitions on the disk you have selected.
Select partition [number]: Replace [number] with the system partition number.
Active
Enter the following command
After the process is successfully completed, restart the computer to check if the operating system can be found.
Method 3. Check BIOS settings
If the system hard drive cannot be recognized by Windows 11/10, a “Operating System not found” prompt will pop up and interrupt the Windows 11/10 startup process. So first, we need to check the BIOS settings to confirm if the BIOS can detect the hard drive, and then determine if the hard drive is damaged.
When opening a Windows 11/10 computer, press the F10/F12 key and release F10/F12 when BIOS SETUP UNITY appears.
- Check the Primary IDE Master, Primary IDE Slave, Secondary IDE Master, and Secondary IDE Master to see if the hard drive is detected.
Has the hard drive been detected
If displayed as “None” or “Not Detected”, the BIOS did not detect the hard drive. Then we can change “None/Not Detected” to “Auto”, which may solve the problem.
Then restart the computer to check if the “Operating System not found” still exists. If the problem persists, you should try other solutions or replace the hard drive.
Method 4. Rebuild damaged MBR
If all the above methods are ineffective, it may be due to MBR corruption causing errors such as “Operating System not found” or “Miss Operating System” in Windows 11/10, so you need to fix MBR. You can run the following command in the command prompt window to fix MBR (open the command prompt window like in Method 3):
Bootrecexe/fixmbr
Bootrecexe/fixboot
Bootrecxe/rebuildbcd
Run the following command in the command prompt window
If you don’t have Windows installation media to access the command prompt, you can use the Aomei Partition Assistant, which allows you to create Windows PE bootable media and easily rebuild damaged MBRs. The specific steps are as follows:
Download software now
Win11/10/8.1/8/7/XP
- Connect a blank USB drive to another Windows computer that can start normally. And download, install, and start the Aomei Partition Assistant on this computer.
- Click “Create Startup Disc” and click “Next” to continue.
Creating a startup disc
- Select “USB Boot Device” in the Start Disc Creation Wizard, and then click “Execute”.
USB boot device
Tip: The USB drive will be formatted, so please backup the USB drive in advance.
After completing the operation, click “Finish”.
complete
- Start your Windows from the WinPE bootable USB drive you created. It includes pre installed Aomei Partition Assistant software, which will automatically run.
- Right click on the system disk and select “Rebuild MBR”.
Rebuild MBR
- Choose the correct MBR type for your current operating system.
Choose the correct MBR type
- Return to the main interface, click the “Submit” button in the upper left corner to preview the upcoming task, confirm it is correct, and then click “Execute” to start rebuilding the MBR.
Submit
After completion, the damaged MBR will be rebuilt. In addition, you can also use this software to activate Windows partitions. Right click on the startup partition, select Advanced Operations>Set as Active Partition.
Start partition
conclusion
The above are four solutions to fix the “Operating System not found” error in Windows 11/10. Obviously, the Aomei partition assistant provides you with a simpler and more comprehensive method.
In addition, it also has many functions for managing disks, such as disk cloning, partition cloning, erasing hard drives, migrating operating systems to SSDs, and so on. Download it now and experience it!
