Tips to fix
1. Check the BIOS
You need to check for two things in the BIOS. Firstly, you need to ensure your machine recognizes your hard drive. Secondly, you need to make sure the drive on which you installed Windows is listed as the preferred boot drive.
The method for entering the BIOS changes from manufacturer to manufacturer. Typically, you'll need to press Escape, Delete, or one of the Function keys during the boot-up process, before Windows loads. You should see an onscreen message advising you which is the correct key during the boot process.
The BIOS menu itself also varies between devices. Broadly speaking, you need to locate the Boot tab at the top of the screen. Unfortunately, you can only use your keyboard to navigate the BIOS menu, so keep an eye out for a list of controls on the BIOS screen.
Within the Boot tab, highlight Hard Drive and press Enter. Make sure Hard Drive is listed above USB Storage, CD\DVD\BD-ROM, Removable Devices, and Network Boot. You can adjust the order using the + and – keys.
If everything in your BIOS menu looked fine, jump to step three. If you didn't see the hard drive listed, go to step two.
2. Reset the BIOS
If your machine is not recognizing your hard drive, there are lots of possible causes. For non-tech-savvy users, the only easy solution is to try resetting the entire BIOS menu to its default values.
At the bottom of the BIOS menu, you should see a key for Setup Defaults or Reset BIOS. On some machines it's F9, but it might be different on yours. Confirm your decision when prompted and restart your machine.
If the operating system is still not found, you can stop reading this article. Unless you know a lot about building computers, you'll need to take your machine to a computer repair shop.
3. Fix the Boot Records
Microsoft Windows primarily relies on three records to boot your machine. They are the Master Boot Record (MBR), DOS Boot Record (DBR), and the Boot Configuration Database (BCD).
If any of the three records becomes damaged or corrupted, there's a high chance you'll encounter the "Operating system not found" message.
Thankfully, fixing these records is not as complicated as you might think. You just need a removable Windows installation drive. Use Microsoft's Media Creation Tool to create some Windows 10 installation media.
When your tool is ready, you need to use it to boot your machine. Depending on your device, you might only need to press a single key during the boot process, or you might have to change the boot order in the BIOS menu.
Eventually, you will see the Windows Setup screen. Enter your preferred language, keyboard, and time format, and click Next. On the next screen, select Repair your computer.
Next, navigate to Troubleshoot > Advanced Options > Command Prompt. When Command Prompt loads, type the following three commands. Press Enter after each of them:
bootrec.exe /fixmbr
bootrec.exe /fixboot
bootrec.exe /rebuildbcd
Each command might take several minutes to complete. Once all the processes are finished, restart your PC and see if it boots successfully.
4. Enable or Disable UEFI Secure Boot
Almost every Windows machine is shipped with UEFI firmware and Secure Boot enabled. However, in some cases, it might not work. For example, if Windows is installed on a GUID Partition Table, it can only boot in UEFI mode. Conversely, if Windows 10 is running on an MBR disk, it cannot boot in UEFI mode.
As such, it's prudent to either enable or disable UEFI Secure Boot and see if it makes a difference. You make the adjustments in the BIOS menu. Usually, the option will be called Secure Boot and can be found in the Security tab.
Regards,
Rachel Gomez
