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Operating system not found: what is this error and how to deal with it. Operating System not found error: what to do

While trying to boot Windows 10, you receive the error: An operating system wasn't found. Try disconnecting any drives that don't contain an operating system.

Press Ctrl+Alt+Del to restart

This error mostly occurs after windows 10 1809 upgrade, or Perform System Restore. And the most probable culprit behind this problem is the corruption of system files. If anything damages your computer's system files, you may find yourself " operating system not found while booting. If you are also struggling from this problem, Here how to fix an operating system wasn't found after restart or system upgrade.

An operating system wasn't found

First of all, Disconnect all external devices include printer, scanner, external HDD and restart windows. Check windows started normally.

Since this error often occurs when BIOS is unable to find the hard drive, checking BIOS settings might be a good solution.

To check the BIOS settings, follow these steps:

Restart the computer
Press the F2 key to open the BIOS menu.
Check the BIOS’ main screen to see whether it detects the hard drive,
Also, check the boot order to see if it is set correctly.
Verify that the hard drive is the first boot device.

If the hard drive is not detected properly, consider replacing the data cables, or resetting the BIOS settings to default values.

Here are the steps to reset BIOS settings:

Enter the BIOS screen by following the steps outlined above
Find the “Reset to default option.
Choose the reset option, and answer “Yes” when prompted for a confirmation
Then, select the “Exit -> Exit saving changes” option.

Perform Windows Startup Repair

The Windows startup Repair may recover certain boot process related errors in some cases. Here are the steps to access the Startup Repair from advanced options. Since due to this problem windows unable to Boot normally, you need a windows installation media to perform next steps. If you don't have check how to create from here.

When you are ready with Windows 10 installation media/USB
Place the Windows Boot Media on the computer and boot from it.
At the first setup screen, choose your Language, Time – Currency and your keyboard input method and click Next.
Now on the next screen select Repair your computer.

This will restart windows now next click Troubleshoot –> Advanced options –> Startup Repair.

Wait while Windows diagnosing and fixing problems. When the Startup Repair is completed this will automatically Restart windows and try to boot in Windows normally.

Repair Corrupted Boot Files

If startup repair failed to fix the problem, then follow the steps below to Configure and Repair the Boot Files.

Again boot from Windows 10 installation media
Once you have reached the Windows Setup screen, press the SHIFT + F10 keys to bring up the Command Prompt.

Now find out whether your disk is set to GUID Partition Table (GPT) or Master Boot Record (MBR):

In the Command Prompt, type diskpart and press Enter.

Now Type list disk and hit the enter key to find out if your disk is set to GPT or MBR partition.

Look at the GPT column to see if it has an asterisk (*).

If you see an asterisk (*), that means that your disk's Partition Table is GPT.
If you don't see an asterisk, that means that your disk's Partition Table is MBR.

Type exit and press Enter.

Now Fallow bellow We have two different solutions for different partitions.

Fix Boot Files on MBR Partition Table

Note: if you have GPT partition skip thi and Fallow next step

Now find out the Drive letter where windows installed. You can do this by command type list volume and hit the enter key. you will notice the Drive letter where windows is installed as Boot.

When you find out which drive contains the Windows folder, (For me its drive “C:”), give the following command to create the boot files on that drive and press Enter.

bcdboot C:\Windows /S C:

* Note: If Windows are located on a different drive, change the letter C with that drive letter.

After execute the command again open DISKPART utility by type command diskpart and hit enter key.
Here on disk part utility type list disk press enter key.
Select the disk letter by using command select disk 0
Type Fallowing commands one by one as per instructed bellow
list volume
select volume 3(Here select the volume number which contains the windows operating system)
active

type exit to close the DISKPART tool. Thats all now remove the installation media and reboot your computer.

Fix Boot Files on GPT Partition Table

If you have the GPT partition Table fallow bellow.

type diskpart and hit enter to open the diskpart utility and type bellow command.

During the loading of the operating system (usually Windows 7,8,10), the user may encounter the system message “An operating system wasn’t found. Try disconnecting any drives that don't contain an operating system. Press Ctrl+Alt+Del to restart". When you press the mentioned keys, the computer restarts, after which this error may occur again. In this article I will tell you what the essence of this problem is, what are its causes and how to fix the error. « An operating system wasn't found" on your PCs.

Screenshot of An operating system wasn't found error.

Translated from in English the text of this message is:

"Operating system not found. Try disabling any drives that do not contain an operating system. Press Ctrl+Alt+Del keys to reboot".

This usually means a situation in which the OS did not find the operating system loader on the “boot” disk (in particular, due to a damaged system partition), and therefore signaled this using the message mentioned above.

In addition to the corrupted system partition, the causes of the problem “An operating system wasn’t found. Try disconnecting any drives that don’t…” there may be insufficiently tight connection of the hard disk cables with the corresponding connectors on the hard drive and motherboard, physical damage to the cables themselves, as well as those connected to the PC external devices(external hard drive, flash drive, 3G modems, connected phones, etc.) without an operating system on them.

How to fix An operating system wasn't found

To solve the problem, first of all, I recommend disconnecting all external drives (flash drive, external hard drive, etc.) from your PC.
Carefully check the tightness of the connection of the hard drive cables to the motherboard, the cause of the problem may be a plug of the corresponding cable slightly detached from the connector.
Go to BIOS and make sure that the hard disk with the operating system is set as the first in the list of boot disks. If it is not in the BIOS settings, install it first in the sequence of boot disks.

If you carefully checked your PC, you did not find any connected flash drives, and the hard drive cables are tight, then to solve the problem “An operating system wasn’t found. Try disconnecting any drives that don't" we need a bootable flash drive (or DVD) with an operating system identical to the one installed on your PC.

Run the following (using Windows 10 as an example):

If the error persists, then do the following:

Now, in accordance with the partition table, we determine the method for fixing the problem.

If you have an MBR

Suppose the Windows OS is located on drive C. Now we enter a command on the command line to create boot files on this disk. We type:

bcdboot C:\Windows /S C:

and press enter. The system should return you the message “Boot files successfully created” (boot files have been successfully created).

Now again we type diskpart in the command line and press enter.

Then we enter list disk and press enter again.

We enter the command select disk 0 and press enter again (0 is the serial number of the disk that contains the operating system).

Then we enter the following commands, not forgetting to press "Enter" after each command:

list volume

select volume X (instead of X, enter the number of the partition on which the OS is installed, usually it has a label like "System reserved" (reserved by the system).

active

exit

Now close all windows and restart your computer by disconnecting external drives (USB flash drive or DVD). The problem can be solved and you can get rid of the "An operating system wasn't found" error on your computer.

If you have GPT

First we need to determine on which disk the Windows OS is installed. Type dir c: at the command prompt and press enter. If you see Windows among the list of directories, then the OS is located on this drive C. If Windows is not there, then enter dir d: and so on until you find the drive where your OS is located.

Suppose the Windows OS is located on drive C. Now we enter the following on the command line, remembering to press enter after each command:

diskpart

list disk

select disk 0 (0 is the number of the disk in order that contains the operating system)

list partition

See which partition has the "system" label. Select the system partition by typing:

select partition X - (instead of X, specify the number of the system partition)

Assign a letter to the system partition using the command:

assign letter=S - (let it be the letter S)

Then type exit and press enter to exit the functionality of the diskpart command.

Now enter the following commands, remembering to press enter after each one:

cd /d S:\EFI\Microsoft\Boot\

ren BCD BCD.bak

bcdboot C:\Windows /l ru-ru /s m: /f UEFI

After that, close all windows, and restart your computer, remembering to remove all external media (flash drive or DVD). The error can be corrected.

Conclusion

The cause of the error "An operating system wasn't found. Try disconnecting any drives that don't contain an operating system. Press Ctrl+Alt+Del to restart" there may be damage to the system partition on which the bootloader is located, which is necessary to start and boot the OS correctly. Use the set of tips I have listed, this will help get rid of the “An operating system wasn’t found” error on your PC.

In contact with

1. Symptoms of the problem

When computer is powered up, the following error message appears:

An operating system wasn't found. Try disconnecting any drives that don't contain an operating system. Press Ctrl+Alt+Del to restart (white-on-black letters in text mode and blinking cursor):

2.Normal boot sequence

The rest of this article refers to Windows 10, but all information below applies to Windows 8/8.1 as well. (Windows 7 and Windows Vista never emit this error, instead they emit "BOOTMGR is missing" .)

Normally Windows 10 boots as shown below:

Master Boot Record scans partition table for active partition, then it loads 1st sector from active partition, verifies 55 AA signature, and transfers control to Boot Sector.
Boot Sector loads 15 additional sectors from the beginning of disk (Volume Boot Record) and transfers control to first additional sector of VBR.
Volume Boot Record loads BOOTMGR file from root directory of boot partition into the memory and transfers control to it.
BOOTMGR loads Boot\BCD registry hive and displays boot menu. BOOTMGR is able to run memory test and set safe mode boot flag per explicit user request. But normally, it loads winload.exe when computer boots normally (cold startup) or winresume.exe (when computer resumes from hibernation).
Winload.exe opens SYSTEM registry hive, gets list of drivers, loads NTOSKRNL.exe, loads drivers (*.SYS files) and transfers control to NTOSKRNL.exe.
Winresume.exe loads memory dump from hiberfil.sys and transfers control to it.

3. Defect in the boot sequence which leads to BOOTMGR is missing error

Defect in the boot sequence which leads to "An operating system wasn't found" error is shown below:

BIOS loads 1st sector from HDD (Master Boot Record), verifies 55 AA signature and transfers control to Master Boot Record.
Master Boot Record scans partition table for active partition. There is one active partition, so Master Boot Record loads 1st sector from active partition (Boot Sector), and transfers control to it.
Boot Sector loads the rest of Volume Boot Record and VBR tries to find BOOTMGR at the root directory of boot partition but fails because "BOOTMGR" file does not exist or not readable.
The rest of the usual boot events do not happen.

4. How to fix "An operating system wasn't found" error

1) Download Emergency Boot Kit and deploy it to USB thumbdrive according to the instructions , then set up your BIOS to boot from USB thumbdrive. You need full version of Emergency Boot Kit to actually write changes to the disk, but it's recommended to try demo version to make sure there are no hardware incompatibilities.

2) Boot into Emergency Boot Kit:

3) Run File Manager from the main menu:

4) Press Alt+F1 and choose your boot partition from the menu. For Windows 10 and Windows 8/8.1 this partition should have "System Reserved" volume label and is expected to be small (100-500MB). Use UP and DOWN arrow keys and ENTER to navigate the menu:

5) In this example, BOOTMGR file is missing from boot partition. If it exists in your environment, delete it (set cursor to the file using arrow keys UP and DOWN and then press F8). If BOOTMGR file is not deleteable, then rename it (for example, to BOOTMGR.OLD by pressing F6 key):

6) Insert Windows 10 installation USB thumbdrive to any of your computer's USB ports and press Alt+F2. Choose Windows 10 installation USB thumbdrive drive from the menu using UP and DOWN arrow keys:

(alternative approach: if don"t have Windows 10 installation USB thumbdrive, then you can recover a copy of this file from \Windows\Boot\PCAT folder on your system partition)

8) Press TAB key to switch input focus to the right panel and navigate to the BOOTMGR file:

9) Press F5 to copy BOOTMGR to the left panel. Confirm with ENTER key:

Very often, when Windows 10 refuses to start, the Boot failure error is displayed on the screen, as well as An operating system wasn’t found. Press Ctrl+Alt+Del to restart. The causes of these errors are the same, the ways to eliminate them are also similar.

In the "top ten" both of these errors may appear. For example, when deleting the bootmgr file on operating systems with Legacy, the first error pops up, and when the entire partition with the bootloader is destroyed, the second error appears.

Before you start troubleshooting, you need to carry out the manipulations that are written in the text of the notification, and then restart the computer. The first step is to disconnect from the PC all drives that do not contain an operating system. These can be flash drives, optical media and third-party hard drives. In addition, everything that is connected via USB can be attributed to this category, except for controls.

In addition, you need to check that the launch is performed from the first hard drive or Windows file Boot Manager for UEFI systems. In this case, you need to go into the BIOS and check the startup order of the devices. To do this, it will be easier to use the Boot Menu. If, when using it, the "ten" starts up normally, then it's worth going to the BIOS and changing the parameters.

If this did not bring the desired result, then such errors occur for more serious reasons, so it will be a little more difficult to eliminate them.

Setting the loader "tens"

As can be understood from the above, the artificial occurrence of errors is a fairly common occurrence if you yourself corrupt the contents of a hidden section reserved by the OS or with the OS loader. In this case, it is necessary to try to restore the OS bootloader when such errors appear.

This can be done quite simply. You need to have a boot drive
or a recovery disk with an operating system of the same bit depth that is installed on the computer. It is worth noting that such a drive can be created on another computer.

Next, you need to boot your PC from this drive. If the installation image of the system is used, then you need to go to the recovery environment. To do this, on the screen for specifying the language, click "System Restore".

Here you need to specify "Troubleshooting". In the next window, click "Advanced Options". After that, you need to click on "Startup Repair". Then you need to select the operating system version.

After that, an automatic search for problems with the bootloader and its recovery will start. This function works perfectly and in most cases no user intervention is required.

If this does not bring the desired result, and the error is again displayed on a black screen, while loading should be performed from the required drive, it is worth trying to reanimate the bootloader in manual mode.

In addition, problems with the bootloader may occur after turning off one of the hard drives from the PC. In this case, the bootloader must be located on this drive, and the operating system on another. In this case, it is necessary to lower in a certain way.

First of all, at the beginning of the disk with the OS, you need to allocate some space for FAT32 for UEFI or NTFS for Legacy. You can do this using the free MiniTool Bootable image. Partition Manager. After that, you need to restore the bootloader manually using bcdboot.exe

Error starting "dozens" due to problems with the hard drive or SSD

If no manipulations to resuscitate the bootloader help eliminate these errors in the top ten, in this case they may be affected by malfunctions with the hard drive or lost files.

If there are suggestions that some of this has happened, and this can be affected by power failures, hard drive defects, etc., in this case, several manipulations are necessary.

The first step is to reconnect the hard drive or solid state drive. To do this, you need to disconnect the SATA cables and power cords from the motherboard and hard drive. You can also disconnect other wires.

Then you need to boot into the recovery environment, and using command line, you need to scan the hard drive for errors. In addition, it is possible to reset the system from a third-party drive. There is also an option to fix the error by installing the operating system from scratch, while performing formatting.

That's basically it possible reasons problems and how to fix them. It will be very good if the problem can be fixed by simply disabling the drives and restoring the bootloader. If this does not help, then you need to reinstall the operating system.

Probably, there is no need to explain how unflattering the situation is when a user turns on a computer or laptop to boot and instead of the usual start, the system writes Operating on the screen for no reason at all. System not found. For many users, this is a real shock. How so? Yesterday, everything worked… What could have happened, and how to fix this situation, we'll see now.

What does the Operating System not found error mean?

If you look at the message itself, it is not difficult to translate it as " operating system not found". But here's the problem - the user is absolutely sure that it exists. But the computer system does not share such confidence with the user, because it simply does not find the components responsible for loading the system.

In general, such situations most often appear, for example, when a user removes a hard drive and replaces it with a new one. Maybe just HDD out of order, but you never know.

Possible causes

If such an incident suddenly turned out, and the system constantly displays the message Operating System not found (Windows 7, 8, etc.), first of all, do not panic. To get started, just check if a flash drive is inserted into the computer or laptop, and in the BIOS settings, the USB device is the priority for booting.

If the hard drive was removed or changed to a new one (this applies to stationary computers), it may very well be that when it was reconnected, the corresponding cables were connected incorrectly or loosely. Let's see what can be done in such a situation.

Basic BIOS settings

by the most in a simple way Changing the BIOS settings can reset all settings to factory defaults (Default). Every BIOS version has this setting.

In extreme cases, you can simply change the boot priority in the Boot Device Priority or Boot Sequence section, and install the hard drive as the first (main) boot device (boot device).

It also happens, however, that the hard drive is detected in the BIOS, but it still does not boot, and the system again and again gives the Operating System not found warning. What to do in such a situation? First, see if it is opposite the hard drive model. It signals that the device in the system, although it is present, is simply disabled or not involved.

As a rule, in most versions of the BIOS on the right there is a special help field for the device (Specific Item Help), which contains a keyboard shortcut that allows you to enable or disable any component. The most likely combination is Shift + 1. But here everything depends on the manufacturer (combinations may be different).

Switching hard drive operating modes in BIOS UEFI

On the other hand, if an Operating System not found warning appears on a laptop, where it is quite problematic to remove the hard drive, you should separately pay attention to the mode settings work hard disk. As an example, consider the settings latest system UEFI, although they can be used in other versions without problems.

In general, there are two main modes in the SATA configuration: AHCI and IDE. During the initial installation of the "OS", as well as in the default settings, it is enabled AHCI mode. When you switch to the IDE, no matter how you try, you won't be able to install Windows on the hard drive.

The same applies to the moments when users, at the end of the installation process, either out of ignorance or accidentally turn on the IDE mode. As it is already clear, the system issues the line Operating System not found. Incidentally, even if this moment put another fully functional “screw”, without changing the SATA settings to the initial ones, it will also not work.

Therefore, it is immediately worth advising users to change such settings only as a last resort, when it is really necessary.

Restoring the Windows bootloader

There are also frequent cases when the message “Operating System not found” appears when the Windows bootloader is damaged, which is associated only with errors on the hard disk, for example, due to incorrect shutdown. In this case, as is already clear, the entire system can “fly off”.

In such a situation, you can try to restore the bootloader, and at the same time check the system disk or partition for errors. To do this, it is always desirable to have the original installation disk or a system recovery disk at hand.

Here you will need to set the optical drive in the BIOS as the first priority boot device, and then use it. Note that in this option there is no question of restoring Windows from a checkpoint. This still won't help and the Operating System not found warning will reappear.

Here you need to use boot recovery mode or command line, which is preferable. In it, you need to sequentially enter two main commands: bootrec.exe /FixMbr and bootrec.exe /FixBoot, after each pressing "Enter". If such a sequence does not help, in addition, you can add the bootrec.exe /RebuildBcd command.

Before performing such actions, it is strongly recommended to check for errors with their automatic correction (commands chkdsk / f / r or chkdsk / f / x / r). You can also use the chkntfs /x c: checker, provided you have a file NTFS systems in the system partition (drive "C").

If nothing helped

However, if all the above methods of correcting the situation do not help, then you should definitely diagnose the hard drive. But if it’s not a problem to remove it, then with a laptop you will have to contact the nearest service center or workshop and not try to remove it yourself.

As it is already clear, if the hard drive “fell down”, there’s nothing to be done, you will have to change it to a new “hardware”, and then install the “OS” again. You can, of course, try out the action of the utility on it, but it is quite difficult to guarantee one hundred percent success.