Hi,
Thank you for writing to Microsoft Community Forums.
It seems like the BCD (Boot Configuration Data) files are corrupted or are moved. These files are responsible for the Operating system on a device. You will need to rebuild BCD. To run the Bootrec.exe tool, first start the Windows RE:
- Put the Windows 10 installation media and then start the computer.
- Boot from the media by pressing the boot key (F2, F12 or Esc, it may differ depending on the motherboard).
- The operating system will load from the media. Once you are on install now screen, please click Repair your computer.
- On the Choose an option screen, select Troubleshoot > Advanced options > Command Prompt.
- Type BOOTREC /FIXMBR, and then press ENTER.
- Type BOOTREC /FIXBOOT, and then press ENTER.
- Type BOOTREC /REBUILDBCD, and then press ENTER.
- Restart your PC.
The above commands should fix the issue. For more information about the commands used, you can refer the article to Use Bootrec.exe in the Windows RE to troubleshoot startup issues. This article is applicable for Windows 10 as well.
Hope it helps,