Fixes for Operating System Not Found/Missing Operating System in Windows 10/8/7

Daisy updated on Apr 28, 2020 to Partition Master | How-to Articles

When the operating system is missing or operating system not found error occurs on your PC, it would be impossible for you to boot up PC or start a Windows system. You'll be presented with a black screen with an error message "Missing operating system.." or "Operating System not found..". Facing this problem, you'll not get any access to Windows 10/8/7 then. So how to fix such a problem? Is it possible to find access or solutions to fix the issue and get the system restored? Let's find out causes and solutions to correct missing operating system error in Windows 10/8/7 now.

Workable Solutions Step-by-step Troubleshooting
Fix 1. Check BIOS Press and hold "F12/F10" to enter BIOS...Full steps
Fix 2. Reboot from a bootalbe disk Press and hold "F10" and press "Power"...Full steps
Fix 3. Set BIOS to default settings Find BIOS and enable the default setup option...Full steps
Fix 4. Rebuild MBR Choose one of the two options to repair...Full steps
Fix 5. Set correct partition active Boot computer with WinPE bootable disk...Full steps

Knowing reasons and causes for how did your computer fail to find the operating system or what makes the operating system not found will make it much easier for you to find the exact solutions to fix this problem and get your Windows system back again. 

Part 1: Reasons/causes for the operating system not found error

  • System/BIOS does not detect Windows installation hard drive/disk
  • System hard disk drive failure due to physical/logical damage
  • Improper/incorrect set BIOS settings
  • Windows Master Boot Record disk is corrupt/damaged
  • Windows boot files in system partition are no longer active

After knowing the top 5 major reasons that cause operating system missing in Windows, you may try to figure out which reason that has caused your Windows OS not found and then find a relative solution to fix the problem.

Part 2: Solutions to fix missing operating system error in Windows 10/8/7

Here you'll find workable solutions to these five problems that cause your computer fails to boot with the operating system not found error.

Solution 1: Check 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 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.

Fix operating system not found error.

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: Test hard disk drive and reboot computer from a WinPE bootable disk

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

Step 2: Use Right Arrow to select the "Tools" menu in BIOS Setup Utility

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

Test hard disk to fix system not found error.

If all tests pass, the hard drive is not damaged. You may jump to Solution 3 to reset BIOS to default state.

If any tests failed, please contact your hard disk or computer manufacturer for a replacement as long as these devices are under warranty.

If you don't want to let the operating system not found issue bother you, you may directly reboot the computer from a WinPE bootable disk. Professional partition manager software - EaseUS Partition Master will help you easily to reboot your computer without any obstacles. You can download it and follow steps to reboot the computer from a WinPE bootable disk now:

Download Now

 Windows 10 is supported

First, create a WinPE bootable disk with another healthy computer:


Step 1: Prepare a disc or drive

To create a bootable disk of EaseUS Partition Master, you should prepare a storage media, like a USB drive, flash drive or a CD/DVD disc. Correctly connect the drive to your computer.

Launch EaseUS Partition Master, go to the "WinPE Creator" feature on the top. Click on it.

create easeus partition master bootable disk

Step 2: Create EaseUS Partition Master bootable drive

You can choose the USB or CD/DVD when the drive is available. However, if you do not have a storage device at hand, you can also save the ISO file to a local drive, and later burn it to a storage media. Once made the option, click "Proceed".

create easeus partition master bootable disk

You have created an EaseUS Partition Master WinPE bootable disk now. You can manage your hard disks and partitions through the bootable drive whenever the computer fails to boot normally.

If you have RAID drives, load the RAID driver first by clicking Add Driver from the menu bar, which can help you add the driver of your device under WinPE environment, as some specific device cannot be recognized under WinPE environment without drivers installed, such as RAID or some specific hard disk.

Then, connect the bootable disk with your computer and reboot it; Select to boot from EaseUS Partition Master bootable disk; Follow the on-screen guidance and you'll get your computer to boot up then.

Then all you need is to wait patiently to let the computer finish system restoring process. If you lost some important data in your computer, you may apply professional data recovery software such as EaseUS Data Recovery Wizard to restore lost data due to the missing operating system error.

Do You Need Specialized Services for System Boot Issues?
EaseUS also provides 1-on-1 remote assistance to fix the boot issue. If the solution above does not work for you, please contact our professionals via Email or LiveChat in this page. To ensure our professional assistance work, you are suggested to connect the unbootable system drive to a healthy computer when getting connected with us.

Solution 3: Set BIOS to default settings

Improper settings or incorrect BIOS setting 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.

Set BIOS to default and fix operating system not found issue.

If this method doesn't work, the MBR disk could be damaged and you may jump to Solution 4 to find the MBR disk repair method.

Solution 4: Repair/Rebuild MBR (Master Boot Record) disk

Here we have two methods to help you repair or rebuild MBR disk: repair MBR with Windows installation disk or repair MBR disk with partition manager software. 

Method 1: Repair MBR disk with Windows installation disk

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

  • Press the "Power" button to turn on PC > Hit "Enter" when Boot from CD prompt
  • Press "R" key in Windows Setup Menu to start the Recovery Console
  • Type: FIXMBR at the C:\> prompt and hit "Enter"
  • Press "Y" key > hit "Enter" when asked if you want to write a new MBR;
  • Restart PC by pressing the "Power" button when the MBR complete write process.
  • Fix MBR to solve missing operating system error.

Method 2: Rebuild/repair MBR disk with partition manager software

If you prefer an easier way to rebuild or repair the MBR disk, you may apply partition manager software - EaseUS Partition Master to repair or rebuild MBR with simple clicks then. 

Download Now

 Windows 10 is supported

Solution 5: Set 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. How to set the correct partition active? You may follow below steps to set boot partition active:

Step 1: Boot computer with WinPE bootable disk created by EaseUS Partition Master.

Step 2: In EaseUS Partition Master window, right-click the boot partition and select "Set active".

Step 3: Follow onscreen guidance to reboot the computer with Windows system then.

All effective solutions for Missing Operating System or Operating System not Found error are all presented to you now. You may try any one methods to fix your problem and get a healthy Windows system back and continue use your computer again.


100% of people found this article helpful.


Frequently Asked Questions

Why Choose EaseUS Partition Master?

"I've used Partition Master Professional many times to create, delete, format, move, rename, and resize partitions."PCWorld

"Partitioning tools have come a very long since the days of complicated command line utilities and EASEUS Partition Master is one of the most advanced programs available."TECH ADVISOR

"I love that the changes you make with EaseUS Partition Master Free aren't immediately applied to the disks. It makes it way easier to play out what will happen after you've made all the changes."Lifewire

Will the "Migrate OS" feature transfer the Windows system files only or the whole C drive?

To ensure that the migrated system will boot normally, the Migrate OS feature will transfer all the files in the system and the boot partitions. Generally, the boot partition is the C drive so the transfer will include all the files in C.

Does EaseUS Partition Master license apply to multiple computers?

The license of Partition Master Professional and Server editions can be used on 1 computer only, while that for for the Technician and Unlimited editions can be used on multiple machines.

What is the difference between EaseUS Partition Master Trial version and the Free version?

Free is for home users only, with most basic functions available such as partition resize and clone. While trial can help you understand how this product works and test what a full license can do on a business or server OS machine.

Will it cause any data loss after resizing the partition in EaseUS Partition Master?

Generally, it will not cause any data loss or boot issue by resizing a partition. However, in order to protect your data, we suggest that you backup the partition before resizing, in case of any unexpected situations such as power outages, computer hardware failures, etc. You can use EaseUS Todo Backup to backup the partition and its trial version is fully functioned for 30 days.

What should I prepare before resizing the partition?

On the partition that is going to be operated, there might be some files being occupied by other programs. To ensure a successful operation, we suggest that you close all the unnecessary software before resizing that partition. Otherwise, EaseUS Partition Master will detect the partition being locked by the other software and require a reboot to resize the partition under boot mode.

About EaseUS Partition Master

All-round disk & partition management software for personal and commercial use. Let it manage your storage drive: resize, format, delete, clone, convert, etc.