When booting up computer, if the BIOS (basic input/out system) fails to find an operating system, one of the above error messages will appear. The error messages, alerts, warnings, and symptoms below are tied to this error.
“Operating System not found” error screen on startup
You can see a error like this “Operating system not found”. When a PC is booting, the BIOS tries to find a operating system on a hard drive to boot from. However, if it is unable to find one, then an “Operating system not found” error is displayed. It may be caused by an error in BIOS configuration, a faulty hard drive, or a damaged Master Boot Record.
Following are the solutions to this issue
Solution 1. Check BIOS settings to see whether it recognize the hard disk or not
1. Restart the machine and press certain key (usually F10, F12, Esc, Del, etc.) to enter BIOS. 2. In BIOS main tab, check whether it detect the Windows installation disk or not. They are Primary Master, Primary Slave, Secondary Master, Secondary Slave, etc.
The methodology for entering the BIOS changes from manufacturer to manufacturer. Typically, you’ll need to press Escape, Delete, or one of the Function keys. You should see an onscreen message advising you which is the correct key during the boot process.
Solution 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 my machine 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.
Solution 3. Run automatic repair
Windows built-in Automatic Repair may repair some boot process related problems in some situations. Here, you should prepare Windows installation disk or Windows repair disk.
1. Boot from the Windows installation disk or Windows repair disk.
2. Choose your language, time and keyboard input and click “Next”.
3. Click on “Repair your computer”.
4. Select “Troubleshot” and then “Advanced” option.
Solution 4. Fix The Boot Records
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.
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