How to Fix Operating System Not Found on Acer?

Get the error message “Operating System not found” on Acer laptop or desktop? Don’t be depressed! You can try methods demonstrated in this paper to fix the issue.


By Bryce / Updated on May 12, 2023

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Can’t boot Acer: Operating system not found

“I can’t access Windows 10 operating system normally and get the error message “Operating System not found” when I turn my Acer laptop on. I have no idea what happens and what should I do? I really need your help. Thanks!”

The analysis and fixes for operating system not found on Acer

The issue operating system not found or missing operating system in Acer can come up mainly out of the following reasons:

▪ There is something wrong with BIOS Settings.
▪ The MBR of the system hard drive is damaged
▪ The system hard drive is corrupted.
▪ Windows system partition is not marked as active.

Based on the events that can account for the warning, you can try one or more of the methods presented in the next context.

✔ Fix 1. Check BIOS Settings

If the issue appears after you adjust the BIOS Settings, the most possible issue can be improper BIOS Settings. Follow the steps below to check BIOS Settings:

1. Restart the Acer computer and press a certain key to enter BIOS.

2. In the BIOS Main Tab, check whether your system disk is detected. If not, change the connection cable to see if it works. If you still get the same error, you can reset the BIOS to default settings.

✔ Fix 2. Repair corrupted MBR

If the issue occurs due to corrupted MBR, you can do as follows to repair damaged MBR via Command Prompt.

1. Boot from Windows installation/repair disk.

2. Choose Langue, Time, and Keyboard input. Then, click Next.

3. In the Install now screen, click Repair your computer.

4. Go to Troubleshoot >Advanced>Command Prompt.

5. Type “bootrec /fixmbr” and press Enter.

If you have no way to access Command Prompt, you can turn to AOMEI Partition Assistant Standard to rebuild MBR. Free download it on a working Windows-based computer, install and run it to create a bootable USB drive or CD , and boot your Acer laptop or desktop from the bootable media. After booting successfully, you will access the main interface of AOMEI Partition Assistant automatically.

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Then, refer to the steps below:

1. Right-click the disk holding damaged MBR and choose “Rebuild MBR”. 

2. Choose a proper MBR type according to your current operating system (Here is Windows 10).

3. Confirm your operation and click “Apply”>“Proceed” to perform it.

After rebuilding MBR, unplug the bootable device, reboot computer, and enter BIOS to boot from the repaired hard drive to see whether the issue still exists.

✔ Fix 3. Set Windows system partition active

If the system partition is no longer active, you can also get a message saying cannot find the operating system on Startup. At this time, you can set the system active to solve it. Here are the detailed steps:

1. Boot your Acer computer from the bootable media made by AOMEI Partition Assistant Standard.

2. In the main console, right-click the boot partition and go to “Advanced”>“Set Active Partition”.

Then, follow the prompts given by AOMEI Partition Assistant to complete the operation. 

After setting partition active, remove the bootable device, reboot the computer from system hard drive.

AOMEI Partition Assistant Standard is suitable for Windows 10/8.1/8/7, XP, and Vista, if you are a Windows Server user, employ AOMEI Partition Assistant Server.
This software is featured with many other functions like extending partition without data loss, copying partition, and so on

Wrap things up

When you encounter Operating System not found error for Acer laptop or desktop on Startup, there is no need to try every method listed above; you can speculate the most possible cause and take corresponding solutions then. If all measures aforementioned are invalid, it is time to turn a certain tool to diagnose the system hard drive. 

Bryce · Staff Editor
Bryce is an editor of AOMEI Technology, he covers backup & restore, hard disk & partitions management, cloud files transfer, website & database backup and so on for AOMEI. He enjoys helping people find solutions to their problems. He loves traveling, Sleeping, reserching and so on. He enjoys helping people find solutions to their problems. He loves traveling, Sleeping, reserching and so on. He would like to spend all time on reaserching computer problems. He is a very cute boy.