An operating system wasn’t found and Boot failure in Windows 10

Two mistakes on a black screen when Windows 10 will not start — «Boot failure. Reboot and Select Proper Boot device or Insert Boot Media in selected Boot device» and «An operating system wasn’t found. Try disconnecting any drives that don t contain an operating system. Press Ctrl+Alt+Del to restart» usually have the same causes and fixes, which will be discussed in the instructions.

In Windows 10, you may receive one or another error (for example, if you delete the bootmgr file on systems with Legacy boot, there is An operating system wasn’t found, and if you remove the entire section with bootloader — error Boot failure select proper boot device).

Before proceeding to the error correction methods described below, try to do what is written in the text of the error message, and then restart the computer (press Ctrl+Alt+Del), namely:

  • Disconnect all drives that do not contain the operating system. Refers to all flash drives, memory cards, CDs. Here you can add a 3G modem and USB-connected phones, they too can affect the system start-up.
  • Make sure that you are booting from the first hard disk or from the file Windows Boot Manager for UEFI systems. To do this, go into the BIOS and in the boot options (Boot) will see the boot device order. Even easier would be to use Boot Menu and, if I use the launch of Windows 10 was OK, to go into the BIOS and change the settings accordingly.

If these simple solutions don’t work, it means that the cause of the appearance of the Boot failure and error An operating system wasn’t found more serious than just not the boot device, we will try more sophisticated ways of correcting the error.

Fix boot Windows 10

As already described above, to artificially cause the described fault, if manually destroying the contents of the hidden partition «reserved system» or «EFI» bootloader for Windows 10. Under natural conditions most often happens also such. Therefore, the first thing to try if Windows 10 says «Boot failure. Select proper Boot device or Insert Boot Media in selected Boot device» or «Try disconnecting any drives that don t contain an operating system. Press Ctrl+Alt+Del to restart» — to restore the operating system loader.

Make it simple, the only thing you need is a recovery disc or bootable USB flash drive (drive) with Windows 10 in the same bitness, installed on your computer. In this case, to make such a disc or USB flash drive you can on any other computer, you can use the instructions: Bootable flash drive Windows 10, Drive Windows recovery 10.

What to do after that:

  • To boot your computer from disk or USB drive.
  • If this is an installation image of Windows 10, it is possible to log in recovery environment on the screen after selecting the language at the bottom left choose «system Restore». Read more: recovery Disk Windows 10.
  • Select «Search and troubleshoot» — «advanced settings» — «startup repair». Also select the target operating system — Windows 10.

Recovery tools will automatically try to find problems with the boot loader and restore it. In my inspections the automatic fix run Windows 10 just fine and works for many situations (including formatting the partition with the boot loader) any manual action will be required.

If that doesn’t work, and after restarting you will again encounter the same error message on a black screen (are you sure you are booting from the correct device), try to restore the boot loader manually: Restore the Windows boot loader 10.

Also possible variant of the problem with the loader after disconnecting one of the hard disks from the computer — in those cases where the bootloader was on that drive, and the operating system on the other. In this case, a possible solution:

  • In the «beginning» of the disk with the system (i.e., before the system partition) to allocate a small partition FAT32 for UEFI boot or NTFS for download Legacy. It can be done, for example, using free bootable image Bootable MiniTool Partition Manager.
  • To restore the boot loader on the partition manually using bcdboot.exe (instructions for manual bootloader recovery was given just above).

Error download Windows 10 because of problems with the hard drive or SSD

If no action to restore the bootloader do not help to fix Boot failure and error An operating system wasn’t found in Windows 10, you can assume the hard drive issues (including hardware) or lost partitions.

If there is reason to believe that there was something of the above (such grounds can be: a power failure, HDD strange sounds, appearing and disappearing hard drive), you can try the following:

  • Reconnect the hard disk drive or SSD: disable the SATA cables and power from the motherboard, disk, reinserted. You can also try other connectors.
  • Once you have booted into the recovery environment using command prompt to check hard disk for errors.
  • Try to reset Windows 10 with an external drive (i.e. bootable disk or USB drive in recovery mode). Cm. How to reset Windows 10.
  • To try a clean install of Windows 10 formatted hard disk.

Hope you can help the first items in the instructions — disable extra drives or restore the bootloader. But if not often have to resort to re-installing the operating system.

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