Missing Operating System: what causes it and how to fix it?

Índice de conteúdos

The error message “Missing Operation System” or “Operating System Not Found” usually appears in a black window when Windows computers start up. This error prevents Windows from starting.

Although it literally means “missing operating system” (or “operating system not found”), this message simply indicates that the Windows operating system has not been found or has boot errors.

Some of the reasons for these errors are: faulty disk, corrupt boot record, BIOS didn’t detect the hard disk, missing or corrupt command.com, virus contamination, etc.

In this article, you’ll find out exactly what can cause the Missing Operating System error and 6 possible ways to solve it.

Missing Operating System

What does Missing Operating System mean?

As we noted at the beginning, Missing Operating System is an error message that means that the operating system installed on your computer (in this case, Windows) cannot be loaded, preventing the PC from booting.

Remember that the general definition of an operating system is software that manages software and hardware resources, allowing them to function correctly, facilitating the process of interaction with users.

What causes Missing Operating System?

Generally, when something goes wrong with the BIOS configuration, disk integrity or the Master Boot Record (MBR), you can’t boot Windows and will encounter Missing Operating System – which reports the same problem in different versions of the operating system.

The causes that can lead to this error are as follows.

  • The basic input/output system (BIOS) does not detect the disk;
  • The disk is damaged;
  • Incorrect BIOS settings;
  • The Windows master boot record (MBR) is corrupted/damaged;
  • An incompatible partition is set as active.

I can’t boot up (Missing Operating System), what do I do?

As various problems can lead to the error, most users don’t know how to start the repair.

In fact, it’s best to start by checking the disk for hardware faults and then dealing with software problems.

1. Check that the disk has been detected by the BIOS

  • Press and hold ” F12/F10″ while pressing the “Power” button to turn on the PC;
  • Release F12/F10 when the BIOS Setup Utility is displayed;
  • Try to find IDE Primary Master, IDE Primary Slave, IDE Secondary Master and check if they can be detectedor not;
  • If no disk is shown or displayed as None/Not Detected, this means that the BIOS has not detected the drive and you can select None to Auto. This may resolve the operating system not found error;
  • If the system disk information is displayed, it means that the BIOS can detect the hard disk and you need to exit the BIOS.

2. Test the Hard Disk for Faults

  • Press and hold “F10” and press the “Power” button to turn on the PC;
  • Release F10 after the PC screen displays a window;
  • Use the right arrow to select the “Tools” menu in the BIOS Setup Utility;
  • Then select “Hard Drive Self Test”;
  • Press “Enter” to start the test.

After the test, you can get two results:

  1. All tests passed: the hard disk is not damaged. You can skip to Solution 3 to reset the BIOS to the default state;
  2. The test failed: you should contact the disk or PC manufacturer for a replacement, as long as these devices are under warranty. If you have important data on the disk, only a professional data recovery company (such as Bot) can remove the data from the damaged disk.

3. Set BIOS To Default State

Improper or incorrect BIOS settings can also cause the Missing Operating System problem on your PC.

In this case, you can try setting the BIOS to the default settings to resolve the fault:

  • Restart the PC and enter the BIOS;
  • Find BIOS and activate the default configuration option, including Load Optimal Defaults, Get Default Values, Load Optimized Defaults, Load Setup Defaults and so on;
  • Press “F10” to save the changes and exit the BIOS.

4. Rebuild the Master Boot Record (MBR)

Both incorrect operation and a virus attack can cause damage to the MBR. When this special boot code (located in the first sector of a hard disk) is damaged, Windows won’t start.

But how can you repair or rebuild the MBR without loading the system? You can use an installation CD/DVD or a Windows repair disk:

  • If you’re using a Windows installation disk, start your computer with it to get the language selection interface, go to preferences and click “Next” to continue;
  • Next, choose “Repair your computer”. Then select a system to repair and click “Next” to get various recovery tools;
  • Here, you can choose “Startup Repair” or “Command Prompt” to do the recovery. However, as the former automatically fixes all the problems that prevent Windows from booting, it requires much more time. So here you should just choose Command Prompt to open a window;
  • When the window opens, type “bootrec/fixmbr” if you only want to fix the MBR. You can also type “bootrec/fixboot” and “bootrec/rebuildbcd” if you want to do more repairs;
  • Finally, exit the Command Prompt safely by typing exit.

After these operations, you can restart your computer to see if the “Missing Operating System” has been resolved.

It is worth noting that, according to Microsoft, the fixmbr command can damage your partition table if there is a virus or if there is a hardware failure.

When the partition table is damaged, existing partitions may become inaccessible, preventing data from being used. If data has been lost in this process, contact a disk recovery specialist.

5. Set the Correct Partition to Active

If Windows is running in Legacy BIOS + MBR mode, the boot partition/system partition must be set to active so that the MBR can pass the boot right to the boot loader and find Windows.

If the system partition or boot partition is not set to active, you may encounter the operating system not found problem.

6. If the disk has problems, recover the data with Bot

If none of these solutions work for your situation, the problem could be quite serious and you may need to reinstall Windows or contact your computer/disk manufacturer for assistance.

Remember that reinstalling the operating system means losing all the data and files saved on your disk.

In this case, to recover them, the ideal is to turn to a specialized recovery service – like Bot.

We at Bot can recover your data safely and efficiently thanks to our more than a decade of experience in data recovery, having successfully handled more than 60,000 cases.

What’s more, we operate in a clean room (certified to US Federal Standard 209): an environment with fully controlled air particles to guarantee the integrity of your disk.


The “Missing Operating System” message is the result of an error that prevents the PC from booting.

This error can be caused by different reasons, including: the BIOS cannot detect the disk where Windows is installed, the disk has a physical or logical failure, the BIOS has been configured incorrectly, a damaged/corrupt MBR or an inactive partition that saves Windows boot files.

To fix this error, you can check whether the disk has been detected by the BIOS, test the disk for faults, set the BIOS to the default state, rebuild the MBR and set the correct partition as active.

In some cases, the failure is only completely corrected after reinstalling Windows – a procedure that erases all the data saved on the PC – leading to the loss of files and documents if you don’t make regular backups.

In this case, to recover your data in complete safety, the ideal is to use a professional restoration service – like the one we offer here at Bot.

The best thing is that you can send your device from any address in Portugal free of charge and have your data evaluated within 48 hours!

Become one of our 99% satisfied customers: start your recovery now.


Posts relacionados