“An operating system wasn’t found” error when booting Windows

Symptoms

When trying to boot Windows, you receive the error:

An operating system wasn’t found. Try disconnecting any drives that don’t contain an operating system.

Press Ctrl+Alt+Del to restart

Resolution

A bootable USB or DVD with Windows 7 or higher is needed to bring up the Command Prompt. If you don’t have a bootable media available, you can obtain one by following the create installation media steps found here.

Step 1: Bring up the Command Prompt:
 

1. Boot from any DVD or USB Windows 7, 8, or 10 media.

2. Once you have reached the Windows Setup screen (where you select the Language, Time and Keyboard settings), press the SHIFT + F10 keys to bring up the Command Prompt.

Step 2: Find out whether your disk is set to GUID Partition Table (GPT) or Master Boot Record (MBR):

1. Within the Command Prompt window, type the following commands, pressing Enter after each command:

   diskpart

   list disk

2. Look for your disk and see if the GPT column has an asterisk (*) – this will indicate the disk is GPT. If no asterisk is found, then the disk is set as MBR.

3. Type exit and press Enter.

Step 3a: If the type is MBR:
 

1. From the Command Prompt, type the following command and press Enter: 

   dir a:

   1. If drive A: is found and a directory is displayed, check for the \Windows folder in the directory. If it is there, that is the System Drive. Skip to step 2.

   2. If drive A: is not found or it doesn’t contain the \Windows folder, type the following command and press Enter:  

      dir b:

   3. Continue through the alphabet until the drive with the \Windows folder is found, but skip the X: drive. That will be the install files from the USB or DVD you are using. The most common location is the C: drive, so that example will be used in the rest of the article.

2. Once it is found, type the following command:

   bcdboot C:\Windows /S C:

   1. In this case, C is the drive where the \Windows folder was found. If the Windows folder is on a different drive, use that drive letter instead of “C” in the bcdboot command above.

3. The message, Boot files successfully created, must be shown before you can continue.

4. Type the following commands, pressing Enter after each command: 

   diskpart

   list disk

   sel disk C

   1. In this case, C is the drive where the \Windows folder was found. If the \Windows folder is on a different drive, use that drive letter instead of “C” in the sel disk command above.

5. Type the following commands, pressing Enter after each command: 

   list vol

   sel vol C

   1. In this case, C is the drive where the \Windows folder was found. If the \Windows folder is on a different drive, use that drive letter instead of “C” in the sel vol command above.

6. Type the following command and press Enter:

   active

   1. You should get a confirmation that the volume has been successfully set as active. If you don’t get the confirmation, it means that either the disk is set to GPT (not MBR), or there is a problem with the disk. Make sure you are working with the right disk.

7. Type the following command and press Enter:

   exit

8. Reboot the device. You can do this quickly from the command prompt by typing the following command and pressing Enter: 

   shutdown -f -r -t 00

Step 3b: If the type is GPT:

1. From the Command Prompt, type the following command and press Enter:

   dir a:

   1. If drive A: is found and a directory is displayed, check for the \Windows folder in the directory. If it is there, that is the System Drive. Skip to step 2.

   2. If drive A: is not found or it doesn’t contain the \Windows folder, type the following command and press Enter:  

      dir b:

   3. Continue through the alphabet until the drive with the \Windows folder is found, but skip the X: drive. That will be the install files from the USB or DVD you are using. The most common location is the C: drive, so that example will be used in the rest of the article.

2. Type the following commands, pressing Enter after each command: 

   diskpart

   list disk

   sel disk C

   1. In this case, C is the drive where the \Windows folder was found. If the \Windows folder is on a different drive, use that drive letter instead of “C” in the sel disk command above.

3. Type the following command and press Enter:

   list part

4. Look for the partition labeled as System.

5. Once it is found, assign the letter R to the partition. If the letter R is already taken, you can choose any unassigned letter. To assign the letter, type the following commands and press Enter after each command:

   assign letter=r:

   exit

6. Return to the Command Prompt, type the following commands one line at a time, pressing Enter after each line:

   cd /d r:\EFI\Microsoft\Boot\

   ren BCD BCD.bak

   bcdboot c:\Windows /l en-us /s m: /f UEFI

   Note: In the last command, /l en-us sets the Windows language to English. To set a different language, replace en-us with a different language code (such as de-de for German).

7. Reboot the device. You can do this quickly from the command prompt by typing the following command and pressing Enter: 

   shutdown -f -r -t 00