How to Fix "An Operating System Wasn’t Found" and "Boot Failure" Errors in Windows

Encountering the “An operating system wasn’t found” or “Boot failure” error when starting up Windows can be alarming, as it may seem like your data is lost. These messages usually indicate that the system cannot locate the OS boot files on the disk. This can be caused by various issues, such as corrupted boot records, a disconnected boot disk, or hardware problems. Let’s go through some steps to troubleshoot and resolve these errors.

1. Check BIOS Settings and Boot Priority

One of the most common reasons for this error is an incorrectly set boot priority. To ensure your computer is booting from the correct disk, follow these steps:

  1. Restart your computer and press the key to enter BIOS (commonly Delete, F2, Esc, or F12, depending on your device model).
  2. In the Boot section, make sure the hard drive with the Windows OS is set as the first boot device.
  3. Save the changes and exit the BIOS.

If the error persists after changing BIOS settings, proceed to the next step.

2. Use Windows Recovery Environment

If Windows fails to boot, you can use the Windows Recovery Environment, accessible through a bootable USB or after multiple unsuccessful start-up attempts:

  1. Connect the bootable USB or installation disk with Windows.
  2. Restart your computer and boot from the installation media.
  3. Select Repair your computer and go to Troubleshoot.

2.1 Repair Boot Sector

Use Command Prompt to restore the boot record:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

These commands help the system locate and repair boot files.

3. Check Hard Drive Health

Hardware issues with the hard drive can also lead to boot errors. Run a check for disk errors using the chkdsk command:

chkdsk /f /r

This command will scan your drive for errors and attempt repairs if any are found.

4. Reinstall Windows (if all else fails)

If the above steps don’t resolve the issue, you may need to reinstall Windows. Be sure to back up any important data before proceeding with a clean installation.