You turned on your Windows 10 and strike with an error screening that “An operating system wasn’t found. Try disconnecting any drives that don’t contain an operating system. Press Ctrl + Alt + Del to restart.” Wondering, what caused this? Here are some common factors which might be the cause for OS not found error in Windows 10.
- When BIOS fails to detect the drive that helps to install Windows
- Hard drive failure
- MBR corruption
- Corruption of partition that holds Windows boot files
What Could be done to fix operating system was not found error on Windows 10?
It tells you to restart the computer by holding Ctrl + Alt + Del button, to solve the issue. Sometimes, you can get your Windows 10 to a normal state by pressing these buttons whereas in some situation it won’t work. Hence, I have listed out some easy techniques which may help you to get rid of OS not found error in Windows 10.
Fix #1: Modify BIOS Settings
Restart your computer and hold down F12 (It will vary depending on the model and OS) to enter BIOS configuration. And, change internal hard drive as first boot device. It will fix OS not found error. If it doesn’t resolve, then try out the next method.
Fix #2: Windows Startup Repair
- Use Windows Boot Media to boot into Windows 10
- When startup screen appears, select appropriate Language, Time, Currency, and keyboard input method and then press Next.
- In the next screen, hit Repair your computer button
- Next, go to Troubleshoot > Advanced options > Startup Repair
- Wait for Windows diagnosing process to complete
It will take some time to complete the process. Don’t do anything while the process is being carried out. Once after completion, you will be able to boot into Windows without any error. It resolves OS not found error.
Fix #: Repair Boot Files
- Boot into Windows 10 using Windows Boot media
- Set Language, Time – Currency and keyboard input method in the setup screen and press Next
- Hold down SHIFT + F10 keys to open the command prompt in the next screen
- Once you open command prompt, next step is to find whether your drive is set to GPT or MBR for that type diskpart and hit enter
- Then type list disk and press Enter
- Locate your disk and then go to GPT column. If it has *, then it indicates that the disk is GPT. If no * means, drive is MBR.
- Exit from the diskpart
In case, disk is set to MBR, follow the steps mentioned below to repair boot files-
- Type dir a: in command prompt and hit Enter.
- When it shows directory list, look for the \Windows folder in the directory.
- If you are unable to locate \Windows folder, then type dir b: and hit Enter button. And, type dir with every alphabet until you find a drive with the \Windows folder. But, don’t use alphabet X drive as it has installation files
- After finding the drive containing \Windows folder, type:bcdboot drivename:\Windows /S drivename: [where drivename is drive letter of the disk in which you have found \Windows folder]
- When you see “Boot files successfully created” message, you can continue with the next steps
- Again type diskpart followed by list disk command in the command prompt
- Next, type sel disk drivename and press Enter [ replace drivename with the drive where Windows folder was found]
- Then, type list vol and hit Enter. Again, type sel vol drivename and press Enter [where drivename is the drive where Windows folder was found]
- Next, type active and hit Enter button
- You will be get notified once the volume is successfully set to active.
If disk is set to GPT, then do as follows-
- Type dir a: and press Enter, in case a is the drive where your \Windows folder is present. If not and you don’t know the drive where your \Windows folder is present, then type dir with every alphabet.
- Next, type diskpart command followed by list disk and press Enter
- Then, type sel disk drivename and press Enter (replace drive name with the drive letter of disk containing Windows folder)
- Next type list part command and hit Enter.
- Now, find the partition that is labeled as System
- Once you find the system partition, name it as R. In case, R is already assigned to some other partition, then use any other alphabets. Type assign letter=r: to assign name to system partition.
- Then, exit and again open command prompt to enter the following command. After each command line hit Enter button.
cd /d r:\EFI\Microsoft\Boot\
ren BCD BCD.bak
bcdboot c:\Windows /l en-us /s m: /f UEFI
Now, exit the command prompt and detach Windows 10 Boot Media. Then, turn on your Windows 10. If you are still getting an error, then reinstall your Windows 10. In case, you end up losing data due to reinstallation, then use data recovery tools and recover lost data from partition of your Windows 10 drive.