“I have a Dell laptop running Windows 10 and it was working well. But suddenly, it
failed to boot and with the error “Missing Operating System” appearing. I’m puzzled
and I have and have no idea what I should to fix Missing Operating System error in
Dell. Is there anyone can offer me some suggestions?”
Analysis of the missing operating system error in Dell
It is common to meet error like “Missing Operating System” or “Operating system not
found occurs in Dell. And you might also encounter such error in Lenovo, HP and so
on. To fix such issue accordingly and quickly, it is necessary to figure out why
operating system is missing. Here are main reasons for “Missing Operating System”
Inappropriate basic input/output system (BIOS) settings
Loose hard drive cable.
Damaged Master Boot Record (MBR) on the system hard drive.
Windows 10 boot files in system partition are not active anymore.
Corrupted system hard drive.
How to fix “Missing operating system” error
If lucky enough, you can settle the issues by quick tricks like restarting computer
or remove all external storage devices such as USB flash drive. If the issue is not
resolved, you can you can take various effective measures listed below after
realizing the causes to “Missing Operating system” in Windows 10.
➢ Way 1. Check cables for the hard drive holds OS
➢ Way 2. Check and adjust the BIOS settings
➢ Way 3. Fix MBR with or without Windows installation disc
➢ Way 4. Set the partition that holds operating system active
Way 1. Check cables for the hard drive holds OS
Windows 10 “Missing Operating System” might happen due to poor connection between
computer and the hard drive. In such circumstance, you can check if the SATA cable
and power cable for the hard drive is loose or damaged. If so, connected the cables
fine or replace it with a good one.
Way 2. Check and adjust the BIOS settings
BIOS tackle with basic setup and boot process. When the hard drive that contains OS
is not detected by BIOS, you can found Missing Operating System in Windows 10.
Follow the steps given below to check the BIOS settings.
1. Press certain key to access BIOS menu while restating computer. The key could be
F1, F10, F12 or Del etc, which can be different in computers made by differential
2. Enter BIOS Setup Utility. Here you can check the Primary IDE Master, Primary IDE
Slave, Secondary IDE Master to see whether the hard drive that Windows installed on
If the system disk is detected, enter Boot menu to ensure that it is set as the first
option for booting.
If it is not recognized by BIOS, you can press certain key (that will be presented in
the BIOS Setup Utility windows) to reset BIOS settings. After that you can press F10
to save changes and exit from BIOS.
Way 3. Fix MBR with or without Windows installation disc
MBR is on the first sector of the disk, which contains the Partition Table and a
small amount executable code for the boot start. If MBR is damaged, you might be
prompted by the error “Missing Operating System”. Here offers two methods for you to
A. Fix MBR with Windows installation disc
If you own Windows installation disc or Windows system repair disc, you can choose
1. Insert the Windows installation disc and boot form it.
2. Navigate to “Repair your computer” >“Troubleshoot” > “Advanced options” >“Command Prompt”
3. Type “bootrec /fixmbr” and hit Enter.
PS.:This command also can be used to fix Invalid Partition Table error in Windows 10.
B. Rebuild MBR without Windows
If you have no Windows installation disc or Windows system repair disc, you can turn
to 3rd party freeware – AOMEI Partition Assistant Standard to fix MBR when you are unable to boot your computer. Free download it and have a closer look at how it
Before you do
Run AOMEI Partition Assistant and use it to create a bootable
media. Then, plug the bootable device into your computer that is unable to
boot and boot your computer from it.
Or you can unplug the disk that contains Windows system and connect it to a
Fix corrupted MBR within three steps
Step 1. In the main user interface, click the disk whose MBR need to
be repaired and choose “Rebuild MBR”.
Step 2. Choose a MBR typed based on the operating system installed on the disk holding damaged MBR and click “OK”.
Step 3.Here you can review your operation. Confirm it and click “Apply” > “Proceed” to perform it.
After fixing MBR, remove the bootable media and boot your computer from the fixed
disk to check whether the error is fixed.
PS.: “Rebuild MBR” will not cause any kind of data loss. It can only
solve problems caused by corrupted MBR. It can’t solve problems caused by bootable
files or system files missing.
Way 4. Set the partition that holds operating system active
If the partition that Windows installed on is not active, you might also receive
error message “Missing Operating System” when starting up your computer. At this
time, to fix “Missing Operating System” in Windows 10, you can set the system active
via AOMEI Partition Assistant.
Step 1. Boot computer from the bootable media created by AOMEI
Partition Assistant and you’ll access the main interface of AOMEI Partition
Step 2. Right-click C drive and go to “Advanced”
> “Set Active Partition”.
Then, you can do as the prompts given by AOMEI Partition Assistant Standard.
Notes: AOMEI Partition Assistant is featured with many other functions, including copy disk, migrate OS to SSD and so on.
Among all the solutions to fix Missing Operating System in Dell, Lenovo, HP and so on, you can try one or more according to your own specific situation. If you are still unable to boot your computer successfully, you can ask the help of the hard drive manufacturer. If your disk is damaged physically, you might need to replace it with a new one.