In order to manually rebuild your BCD, please follow the steps below:_ -Boot your PC/laptop in recovery mode.  -Now, you need to launch the ‘Command Prompt’ in the list of ‘Advanced Options’. -In order to rebuild BCD, use the command ‘bootrec/rebuildbcd as it will then start scanning your operating systems and let you choose the Operating System of your choice which you wish to add to BCD. -Just wait for the command to get completed and then you are good to go.