“Missing operating system” or “Operating System not found” is an error usually appears when you just start up your computer. It is terrifying in that they tell you your computer cannot find your operating system and you are really unable to go any further.
These errors can result from corrupted Boot Configuration Data (BCD), problematic BIOS configuration, faulty hardware, etc. And if you encounter this error, don’t worry! You can try the methods below to see if they fix your problem.
2) Set the system partition active
* Note that you need to have a Windows Installation media (this includes a DVD or a USB drive with Windows Installation package inside) before you go into any following troubleshooting.
1) Rebuild BCD
Missing operating system may come from boot loading issues. You can try rebuilding BCD and see if this solves the problem.
a) Boot from your Windows installation media.
b) After selecting the language and region, click on Repair your computer.
c) For Windows 10, select Troubleshoot and then Command Prompt.
d) For Windows 7, select the first item and then the Windows 7 system. Click on Next. After that click on Command Prompt.
e) In Command Prompt, type “bootrec /rebuildbcd” and hit Enter. If you are asked whether you want to add a new installation to boot list, enter Y.
f) Close Command Prompt and restart your computer. Check and see if the Missing operating system error is gone.
2) Set the system partition active
When you see an Operating System not found error, it is possible that the partition containing your operating system is not active. Therefore you need to set the system partition to active.
a) Go through steps a to c or d in method 1 to open Command Prompt.
b) Type “diskpart” and hit Enter. Then Type “list disk” and press Enter.
c) A list of disks appears. At this point, type “select disk # (“#” here refers to the number of the disk where you have installed your system)” and hit Enter.
d) Type “list partition” and press Enter. This will show a list of partitions in this disk. Then enter “select partition # (“#” here refers to the number of the System Reserved partition, where the boot loader is located. Usually it is the smaller primary partition)”.
e) Type “active” and hit Enter.
f) The system partition is set to active. Type “exit” to exit diskpart and close Command Prompt. Then restart your computer and see if the Operating System not found problem resolves.
3) Configure BIOS
The problems in BIOS can also be the cause of your Operating System not found issue. You need to check and reset its configuration to solve the problem.
* Note that configuring BIOS is an advanced and complicated job. Improper operation can bring about unexpected consequences. You may need to ask a computer expert for help if you are not familiar with BIOS.
a) Enter BIOS.
b) Check the boot order in BIOS and make sure your hard drive is properly detected.
c) If you cannot find your hard drive, you can reset BIOS settings to default configuration and restart your computer.
d) If the step above does not work, you may need to check your hardware status.
4) Check your hardware
If none of the methods above help you solve your problem, you may need to consider it as a hardware issue. You can test with another data cable, or even another hard drive. If you encounter any hardware problem that you cannot deal with yourself, it is recommended that you contact your device manufacturers for further assistance.