" Unable to find an operating system " is an error that occurs during system startup and appears with a message on a black screen, the kind that prevents any operation of accessing the Windows desktop. The situation seems initially frightening and quite complicated, however, just like many other Windows errors, this can be resolved without having to bring the PC to the technician and without having to reinstall it all over again. Usually it occurs if an error has been made in the management of the disk partitions or even following a particularly serious malware infection.
This problem can occur in any version of Windows and if it derives from a software problem it can be preceded by slowness of the PC, program crashes, freezes and similar problems. In addition, before the error arises, the system may present itself at startup with the recovery options and when you select to restart the PC, the system generates the error " Operating system not found ".
If this were not the cause of the error, then the error may have been triggered by various problems such as:
- Master Boot Record (MBR) corruption
- DOS Boot Record (DBR)
- Boot Configuration Database (BCD)
- Disabling the system partition.
It may be that the BIOS cannot detect the Windows installation disc or that the BIOS settings are set incorrectly. So if you get a black screen during Windows startup with an operating system error not detected message, let's see how to fix the error immediately and go back to loading the operating system.
This solution requires having Windows 10 installation media on DVD or USB at hand. To get Windows 10 just download the Media Creation Tool from the Microsoft website and then create the system installation USB stick.
Keeping the key with the Windows 10 installation files connected to the PC, restart the computer and set it to load from the USB stick instead of from the disk. (see How to boot your computer from USB).
When the first screen of the Windows 10 installation procedure is displayed, go Next and then, on the second screen, click the link below Repair your PC .
In the options screen, press on the Troubleshooting box.
Go to Advanced Options and open the Command Prompt.
In the command prompt window, just type the following commands by pressing Enter after each one:
bootrec.exe / fixmbr
bootrec.exe / fixboot (this command may fail due to permission problems, but it does nothing).
bootrec.exe / rebuildbcd
Reboot your PC
In case the PC still doesn't work, we have seen in another article a thorough guide to restore MBR, boot loader and computer startup
From the Windows 10 installation menu, go to the first language selection screen and then press on Repair the PC in the second screen without starting the installation.
In the screen that appears, press the Troubleshoot button and then, in the Advanced Options, click to open the Command Prompt.
Then type the diskpart command in the command prompt window and press Enter.
Then write list disk, press Enter, and then select disk n (the n stands for the disk number where the operating system is located, usually it is disk 0).
Give the list volume command to see the disk partitions.
Locate the partition where the Windows operating system is present (based on the size it should be easily found and write the command select volume n (at the post of n put the right partition number).
To activate the selected partition, write the active command in the command prompt window and press Enter.
Close everything and restart your PC.
To do this, simply access the PC BIOS by pressing the corresponding key (usually one of the Function keys F1, F2, F10, F11 or F12 or the Del key or the Esc key).
In the BIOS, look for the PC boot or boot screen and change the BIOS setting from Legacy to UEFI.
Also, look for and check that the Secure Boot option is disabled and, if necessary, disable it.
Press F10 to save the changes and restart the PC.
READ ALSO: Black screen error with cursor when starting the Windows PC: solutions
This problem can occur in any version of Windows and if it derives from a software problem it can be preceded by slowness of the PC, program crashes, freezes and similar problems. In addition, before the error arises, the system may present itself at startup with the recovery options and when you select to restart the PC, the system generates the error " Operating system not found ".
Article Index
- Disconnect USB stick
- Correct MBR
- Activate the Windows partition
- Activate UEFI
Quick resolution test
In fact, in some cases this error can be easily and trivially resolved by detaching any USB sticks connected to the computer. In fact, it may be that the boot order of the PC is set to load first from the removable drive instead of from the internal main disk (SSD or Hard Disk). By disconnecting the USB stick (for safety it is better to disconnect all external devices connected to the USB ports of the PC) and restarting the computer, then the PC will return to load the Windows 10 operating system installed on the disk.If this were not the cause of the error, then the error may have been triggered by various problems such as:
- Master Boot Record (MBR) corruption
- DOS Boot Record (DBR)
- Boot Configuration Database (BCD)
- Disabling the system partition.
It may be that the BIOS cannot detect the Windows installation disc or that the BIOS settings are set incorrectly. So if you get a black screen during Windows startup with an operating system error not detected message, let's see how to fix the error immediately and go back to loading the operating system.
Method 1: Correct MBR / DBR / BCD
Correcting errors on MBR, DBR and BCD is the most effective solution, which should resolve the error. Cannot find an operating system permanently and without consequences.This solution requires having Windows 10 installation media on DVD or USB at hand. To get Windows 10 just download the Media Creation Tool from the Microsoft website and then create the system installation USB stick.
Keeping the key with the Windows 10 installation files connected to the PC, restart the computer and set it to load from the USB stick instead of from the disk. (see How to boot your computer from USB).
When the first screen of the Windows 10 installation procedure is displayed, go Next and then, on the second screen, click the link below Repair your PC .
In the options screen, press on the Troubleshooting box.
Go to Advanced Options and open the Command Prompt.
In the command prompt window, just type the following commands by pressing Enter after each one:
bootrec.exe / fixmbr
bootrec.exe / fixboot (this command may fail due to permission problems, but it does nothing).
bootrec.exe / rebuildbcd
Reboot your PC
In case the PC still doesn't work, we have seen in another article a thorough guide to restore MBR, boot loader and computer startup
Method 2. Activate Windows partition
If the previous method did not work, the Windows partition may have been disabled by mistake or due to software. To activate the Windows partition, we return to boot the PC from the USB stick with the Windows 10 installation files as seen in the previous point.From the Windows 10 installation menu, go to the first language selection screen and then press on Repair the PC in the second screen without starting the installation.
In the screen that appears, press the Troubleshoot button and then, in the Advanced Options, click to open the Command Prompt.
Then type the diskpart command in the command prompt window and press Enter.
Then write list disk, press Enter, and then select disk n (the n stands for the disk number where the operating system is located, usually it is disk 0).
Give the list volume command to see the disk partitions.
Locate the partition where the Windows operating system is present (based on the size it should be easily found and write the command select volume n (at the post of n put the right partition number).
To activate the selected partition, write the active command in the command prompt window and press Enter.
Close everything and restart your PC.
Method 3: Enable UEFI and disable Secure Boot
In some cases, the error in reporting the missing operating system can occur on a system that starts with BIOS in Legacy and non-UEFI mode . We have seen that when the disk partition style is GPT, the PC will only boot if the BIOS boots in UEFI mode and not in Legacy mode.To do this, simply access the PC BIOS by pressing the corresponding key (usually one of the Function keys F1, F2, F10, F11 or F12 or the Del key or the Esc key).
In the BIOS, look for the PC boot or boot screen and change the BIOS setting from Legacy to UEFI.
Also, look for and check that the Secure Boot option is disabled and, if necessary, disable it.
Press F10 to save the changes and restart the PC.
READ ALSO: Black screen error with cursor when starting the Windows PC: solutions
