By Ailsa / Last Updated May 15, 2020

Why Operating System Not Found in Windows 10?

Do you have the experience that the "Operating System Not Found" or "Missing Operating System" error message occurs to your computer? You must be shocked in panic, and don’t know the reason why there is no Operating System found? However, we have to figure it out. How to find Operating System in Windows 10 and repair your Operating System without data loss?

First of all, you should figure out why the message occurred to your computer, which makes this error easier to solve.

There are some reasons for Operating System missing in Windows 10:

  • The system hard disk is damaged.

  • The basic input/output system (BIOS) does not detect Windows 10 Installation hard drive/disk.

  • Windows 10 boot files in system partition are not active anymore.

  • The MBR (Master Boot Record) of Windows 10 is corrupted.

There are several methods to repair Operating System in Windows 10, here we go.

4 Methods to Repair Windows Operating System

Method 1: Check the BIOS Settings

If the system hard disk cannot be recognized by Windows 10, you will discover the Operating System Not Found in Windows 10. Check the BIOS settings to make sure the BIOS whether detect the hard disk or not, then determine if the hard disk is damaged.

  • Press F10/F12 key while turning on the Windows 10 computer.

  • Release F10/F12 when the BIOS SETUP UTILITY shows up.

  • Check the Primary IDE Master, Primary IDE Slave, Secondary IDE Master, and Secondary IDE Master to see if the hard disk is detected.

BIOS Settings

If displayed as "None" or "Not Detected", that is to say, the BIOS does not detect the hard disk, you could change "None/Not Detected" to "Auto". Maybe it solves this problem.

Restart your computer to test your problem. If the problem still there, you should try other solutions or replace it.

Method 2: Create A Bootable Media and Reboot From It

Creating a bootable media is another way to restore your Windows 10 OS to normal, so how to create a bootable media? Maybe you could use Partition Assistant to make a bootable USB with another normal computer.

1. Download AOMEI Partition Assistant Standard, Install and launch the program.

2. Click "Make Bootable Media" under the left "Wizards" column, a window pops up, click "Next".

Make Bootable Media

Make Bootable Media Notice

3. In next window, choose "USB boot device", then press "Proceed".

WinPE Bootable Media

Tips: USB drive will be formatted, so make sure backup your important files to another location with AOMEI Backupper.

Format USB Notice

4. Click "Finish" when the operation is done.

Create Bootable Media Finished

5. Insert the Partition Assistant bootable media and enter BIOS to set it as the first boot device, and then follow the guidance to boot up.

6. Then the system will be restored. That is to say, the Operating System not found issue has been repaired.

Method 3: Set the System Partition Active

When the system partition is no longer active, you may see the message says "Missing Operating System" when boot up your Windows 10 computer. So set the system partition active to fix it.

  • Boot computer from your bootable media created by Partition Assistant.

  • In the Partition Assistant main console, right-click the boot partition, select "Advanced"->"Set Active Partition".

Set Active Partition

  • Then follow the instructions to reboot.

Method 4: Rebuild MBR with Partition Assistant

You can use Fixmbr command to rebuild MBR, search for on the Internet if interested, by the way, the Fixmbr is supported only on X86-based computers.

There is another easier option-rebuild MBR with Partition Assistant, there are just 3 steps to fix it.

After these operations, Operating System Not Found in Windows 10 issue will be fixed.

Above all are the solutions to fix missing Operating System in Windows 10, you will find the best way to solve this problem. Besides, AOMEI Partition Assistant provides more functions to manage disk, like disk copy, partition copy, wipe hard drive, migrate OS to SSD, quick partition and so on.