Why is my computer not showing the second Windows boot option? - MR-SIR2525/documentation GitHub Wiki

Assuming you have 2 SSDs (or drives), here are some common issues and solutions:

or jump to Repair/Add entry in Boot Configuration Data (BCD)

  1. BIOS/UEFI Settings:

    • Restart your computer and enter the BIOS/UEFI settings (typically by pressing a key like F2, Del, F10, or Esc, depending on the manufacturer).
    • Look for a boot menu or boot order settings.
    • Ensure both SSDs are recognized and listed there.
    • Adjust the boot order to include the second SSD if it's not listed.

  2. Boot Manager:

    • Windows uses the Boot Configuration Data (BCD), which might not have an entry for the second SSD.
    • You can use tools like bcdedit in Windows or a third-party boot manager to add an entry for the second SSD.

  3. Fast Boot:

    • If Fast Boot is enabled in the BIOS/UEFI or within Windows, it might skip the boot selection menu.
    • Try disabling Fast Boot in the BIOS/UEFI and within Windows (Control Panel > Power Options > Choose what the power buttons do > Change settings that are currently unavailable > Uncheck Fast Startup).

  4. Windows Update or System Changes:

    • Sometimes, a Windows update or system changes can alter the BCD or boot settings.
    • If the second boot option disappeared after an update or change, this could be the reason.

  5. Disk Issues:

    • The second SSD might have a problem that prevents it from being recognized as a bootable device.
    • Check the SSD's health and connection.

  6. Secure Boot:

    • If Secure Boot is enabled, it may prevent booting from an unrecognized or unsigned system.
    • Check Secure Boot settings in the BIOS/UEFI and consider disabling it temporarily to test if this is the cause.

  7. Manual BCD Edit:

    • You can manually edit the BCD store using the bcdedit command in an elevated Command Prompt.
    • Back up your existing BCD store before making changes.

  8. Hardware Issues:

    • There might be a hardware issue with the SSD or the connection. Ensure the SSD is properly connected and recognized by the system.

  9. MBR/GPT Conflict:

    • If one drive is using MBR and the other GPT, this could potentially cause issues. Make sure both drives are using the same partition style that your system supports.

  10. Check for a Key to Access Boot Menu:

    • Some systems have a separate key (like F12) to directly access the boot menu. Press this at startup to see if you can select the second SSD.

Repair/Add entry in Boot Configuration Data (BCD)

If the second Windows boot option isn't listed in the UEFI and you suspect it's a BCD issue, you can try to repair the Boot Configuration Data:

  1. Boot into the Windows installation that you are able to.

  2. Open Command Prompt as Administrator:

    • Right-click on the Start button and select "Windows Terminal (Admin)" or "Command Prompt (Admin)".

  3. Check Existing BCD Entries:

    • Type bcdedit /enum and press Enter to list the current BCD entries.
    • Look for entries for the Windows installations. If the second one is missing, you'll need to create a new entry for it.

  4. Identify the Drive:

    • Determine the drive letter of the second SSD’s Windows partition by using diskpart or by looking in "This PC" in File Explorer.

  5. Add BCD Entry for the Second Windows Installation:

    • Use the bcdboot command to create a new BCD entry: 
      bcdboot X:\Windows
      Replace X: with the actual drive letter of the second SSD's Windows partition.

  6. Reboot and Check Boot Menu:

    • After adding the new BCD entry, restart your computer and check the UEFI/BIOS boot menu to see if the second Windows installation appears.

If You Can’t Access the Second Windows Installation:

If the second SSD with Windows isn't accessible, or if you prefer to perform BCD repairs from outside the operating system environment, you can use a Windows installation media to repair the BCD:

  1. Insert the Windows Installation Media and reboot your computer.

  2. Boot from the Installation Media:

    • Press the key that opens the boot device menu during startup (commonly F12, F9, F10, or Esc).
    • Select your installation media from the boot menu.

  3. Repair Your Computer:

    • On the Windows Setup screen, click "Next", then choose "Repair your computer".

  4. Troubleshoot > Advanced Options:

    • Choose "Troubleshoot" and then "Advanced Options".

  5. Open Command Prompt:

    • Select "Command Prompt" from the list of advanced options.

  6. Follow Steps 3-5 Above:

    • Use the bcdedit and bcdboot commands as described above to create a new BCD entry for the second Windows installation.

Repairing the BCD can resolve issues with boot options not appearing. However, be cautious when using these tools, as incorrect commands can affect the bootability of your system. Preferably, don't mess with the boot settings for the Windows installation that you are currently operating on.