Causes of the ‘Operating System Not Found’ Error
There are some simple reasons this could happen, and it’s unlikely that your important data has been erased. Here are some causes for this error:
BIOS has been misconfigured Boot records are damaged The hard drive is damaged or unreachable
How to Fix the ‘Operating System Not Found’ Error
This is important because if something else like a flash drive or disc has priority but doesn’t have an operating system on it, your computer will assume that there isn’t an OS to boot to, and it will throw the “not found” error. You do this through the BIOS setup utility (see the link in Step 3 to learn how to get there) through the Security tab. Toggle Secure Boot to whatever it currently isn’t, so either Enabled or Disabled. Restart your computer after this step. If you’re still seeing the “Operating System not found” error, revert this setting back to what it was and continue with the next suggestion below. The easiest way to fix the “Operating System not found” error with a BIOS reset is to look for a reset option within the BIOS setup utility. It might be a function key like F9 that you need to press, or a menu option called Reset BIOS. The specific steps you need to take depend on the BIOS manufacturer. Start by rebuilding the BCD with this command (open that link for all the steps you need to get to the Command Prompt where you can type this): While you’re still in Command Prompt, after the previous command finishes, enter this one: Finally, reboot your computer to see if the “Operating System not found” error has been fixed. Access Command Prompt from the installation CD by following the same steps as above, and then enter this command: Followed by: Use this command to pick the disk that corresponds to the one the operating system is installed on (most people will see just one in the list): Enter this to list all the partitions on that disk: Use this command to pick the partition on that disk that Windows is installed on: Make the volume active with this command: If you’ve fixed the “Operating System not found” error, Windows should start normally when you reboot. Exit Command Prompt and choose Continue to try starting the operating system. If you can’t access the hard drive to reinstall the operating system, Step 10 is your last option.
