A practical guide for adding another Windows 10 or Windows 11 installation to Windows Boot Manager without reinstalling the system or deleting existing boot entries.
If you have two Windows installations on one computer, the Windows Boot Manager can show a startup menu where you choose which system to load. This is useful when you have Windows 10 and Windows 11 on different partitions, two separate SSDs, a cloned Windows installation, or a test copy of Windows that does not appear in the boot menu automatically.
The safest way to add an existing Windows installation to the boot menu is usually to use bcdboot. This tool copies the required boot files and creates a Boot Configuration Data entry for the selected Windows folder. For advanced cases, bcdedit can be used to edit the boot menu manually.
You usually need this procedure when Windows is installed correctly, but the boot menu does not list it. Common scenarios include:
You installed Windows on another physical drive, but the PC always starts only one system.
You have two Windows folders on different partitions, for example C:\Windows and D:\Windows.
A cloned system is present on disk, but it was not automatically added to the Boot Configuration Data store.
A Windows update, disk operation, or recovery command removed one of the operating systems from the menu.
Windows folder, adding a boot entry will not repair the operating system itself.
Boot configuration changes are normally safe when you use the correct drive letters, but a mistake can make the PC start the wrong system or hide the boot menu. Complete these checks first.
Windows folder.clean, format, delete partition, or disk conversion commands are not required for adding a boot menu entry. Do not run them unless you intentionally want to erase or restructure a disk.
Windows Boot Manager reads startup entries from the Boot Configuration Data store, usually called BCD. Each Windows installation shown in the boot menu has its own loader entry. That entry points to the Windows partition and to the loader file used to start the operating system.
| Component | What it does | Typical value |
|---|---|---|
| Windows Boot Manager | Displays the boot menu and starts the selected loader entry. | {bootmgr} |
| Windows loader entry | Points to a specific Windows installation. | {current} or a GUID |
| Device and OS device | Tell the boot manager which partition contains Windows. | partition=D: |
| Loader path | Defines the startup loader file. | \Windows\system32\winload.efi |
| Timeout | Controls how many seconds the boot menu stays visible. | 10 seconds |
On a modern UEFI/GPT computer, Windows boot files are normally stored on the small FAT32 EFI System Partition. On an older Legacy BIOS/MBR computer, boot files are stored on the active system partition. The commands below cover both cases, but most Windows 11 installations use UEFI/GPT.
The most important step is to identify the correct drive letter of the second Windows installation. In normal Windows, it may appear as D:, E:, or another letter. In recovery mode, the letters can be different.
Command Promptdir D:\Windows
dir E:\Windows
dir F:\Windows
If the command shows folders such as System32, WinSxS, and explorer.exe, that drive probably contains a Windows installation.
If you are not sure which partition is which, list volumes:
Command Promptdiskpart
list volume
exit
Look at the size, file system, and label. The second Windows partition is usually a large NTFS volume, while the EFI System Partition is usually a small FAT32 volume.
C:\Windows and the second Windows installation is assumed to be D:\Windows. Replace D: with the actual letter on your PC.
This is the recommended method when one Windows installation already starts normally and you simply need to add another existing Windows installation to the menu.
Use this when Windows starts and the second Windows folder is visible from File Explorer or Command Prompt.
Fastest methodNo third-party boot manager is needed. The command updates the Windows Boot Manager configuration.
Built-inThe /d option helps preserve the current default boot entry instead of automatically switching it.
dir D:\Windows.bcdboot for the second Windows installation.Command Promptbcdboot D:\Windows /d /addlast
In many same-PC dual-boot setups, this is enough. The command uses the existing system boot partition and adds the second Windows installation to the boot configuration.
D:\Windows is the Windows folder you want to add. /d keeps the existing default operating system. /addlast is useful on UEFI systems because it adds the firmware boot entry after existing entries instead of moving it to the top.
If you are repairing a more complex configuration or working from recovery mode, you can mount the EFI System Partition and specify it explicitly.
Command Promptdiskpart
list volume
select volume 2
assign letter=S
exit
bcdboot D:\Windows /s S: /f UEFI /d /addlast
Replace select volume 2 with the actual number of the small FAT32 EFI partition. Do not select the large Windows partition by mistake.
On older Legacy BIOS systems, specify the active system partition instead of the EFI partition:
Command Promptbcdboot D:\Windows /s S: /f BIOS /d
Use this only if the computer is really booting in Legacy BIOS mode. On UEFI/GPT systems, use the UEFI command instead.
Use this method if the main Windows installation does not start, if you are working after disk cloning, or if you need to repair the boot menu from outside Windows.
bcdboot with the correct letters.Drive letters in WinRE often differ from normal Windows. Always check them again:
Command Promptdir C:\Windows
dir D:\Windows
dir E:\Windows
Then mount the EFI System Partition and create the boot entry:
UEFI / GPT examplediskpart
list volume
select volume 2
assign letter=S
exit
bcdboot D:\Windows /s S: /f UEFI /d /addlast
D:\Windows works in normal Windows but not in WinRE, try C:\Windows, E:\Windows, and other letters. The correct letter is the one that contains the target Windows folder in the current recovery session.
Use manual bcdedit only when bcdboot is not suitable or when you need full control over the boot entry. This method copies an existing Windows loader entry and changes it to point to the second Windows partition.
device, osdevice, or loader path can create a boot menu item that fails to start. Use bcdboot first unless you specifically need manual editing.
Command Promptbcdedit /enum
Command Promptbcdedit /copy {current} /d "Windows 11 - Second SSD"
The command returns a new identifier similar to {12345678-1234-1234-1234-123456789abc}. Use your returned identifier in the next commands.
UEFI examplebcdedit /set {NEW-GUID} device partition=D:
bcdedit /set {NEW-GUID} osdevice partition=D:
bcdedit /set {NEW-GUID} path \Windows\system32\winload.efi
bcdedit /set {NEW-GUID} systemroot \Windows
bcdedit /displayorder {NEW-GUID} /addlast
Replace {NEW-GUID} with the identifier returned by the copy command, and replace D: with the real partition letter of the second Windows installation.
If the computer boots in Legacy BIOS mode, the loader path is usually:
Legacy BIOS loader pathbcdedit /set {NEW-GUID} path \Windows\system32\winload.exe
Do not mix winload.efi and winload.exe. Use the loader type that matches the computer's actual boot mode.
After adding the second Windows installation, both entries may have similar names such as Windows 11 or Windows 10. Rename them so you can clearly identify which one is on which drive.
Command Promptbcdedit /enum
Command Promptbcdedit /set {current} description "Windows 11 - Main SSD"
Command Promptbcdedit /set {NEW-GUID} description "Windows 10 - Second SSD"
Command Promptbcdedit /default {current}
To make the second Windows installation the default, use its GUID instead:
Command Promptbcdedit /default {NEW-GUID}
Command Promptbcdedit /timeout 10
A value such as 10 gives you enough time to choose the system. A value of 0 can hide the menu and immediately start the default entry.
| Problem | Likely cause | Fix |
|---|---|---|
Failure when attempting to copy boot files |
Wrong Windows drive letter, locked BitLocker volume, missing EFI partition letter, or not running as administrator. | Check dir D:\Windows, unlock BitLocker if needed, mount the EFI partition as S:, and run Command Prompt as administrator. |
| The second Windows entry appears but does not boot | The entry points to the wrong partition or uses the wrong loader path. | Recreate the entry with bcdboot D:\Windows /d or correct device, osdevice, and path. |
| No boot menu appears | Timeout is set to 0, only one entry is active, or the menu is hidden. |
Run bcdedit /timeout 10 and bcdedit /set {bootmgr} displaybootmenu yes. |
| BIOS/UEFI starts the wrong disk | The firmware boot order points to another drive or another Windows Boot Manager entry. | Open BIOS/UEFI setup and put the correct Windows Boot Manager entry first. |
| The second Windows asks for BitLocker recovery | Boot configuration or firmware state changed, and BitLocker protection was triggered. | Enter the recovery key, then suspend and resume BitLocker protection from the Windows you use. |
The boot configuration data store could not be opened |
Command Prompt is not elevated, or you are editing the wrong offline store. | Run Terminal as administrator, or specify the correct BCD store only if you intentionally work offline. |
If you no longer need the second entry, remove only the boot menu item first. Do not delete the partition until you confirm that the remaining Windows installation starts correctly.
Command Promptbcdedit /enum
Then delete the unwanted entry by its GUID:
Command Promptbcdedit /delete {NEW-GUID}
{current} while you are booted from that Windows installation. If you are not sure which entry is safe to remove, rename entries first and reboot once before deleting anything.
| Task | Command | When to use |
|---|---|---|
| Check the second Windows folder | dir D:\Windows |
Before adding any boot entry. |
| Add second Windows automatically | bcdboot D:\Windows /d /addlast |
Most normal dual-boot setups from a running Windows system. |
| Add second Windows to mounted EFI partition | bcdboot D:\Windows /s S: /f UEFI /d /addlast |
UEFI/GPT repair or recovery mode. |
| Add second Windows on Legacy BIOS | bcdboot D:\Windows /s S: /f BIOS /d |
Older BIOS/MBR installations only. |
| Show all boot entries | bcdedit /enum |
To find GUIDs and descriptions. |
| Rename current entry | bcdedit /set {current} description "Windows 11 - Main SSD" |
To make the boot menu understandable. |
| Set timeout | bcdedit /timeout 10 |
When the menu disappears too fast. |
| Force menu display | bcdedit /set {bootmgr} displaybootmenu yes |
When multiple entries exist but the menu is hidden. |
| Remove an unwanted entry | bcdedit /delete {NEW-GUID} |
Only after confirming the correct entry by GUID. |
bcdboot erase the second Windows installation?
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bcdboot copies boot files and creates or repairs boot configuration entries. It does not format the Windows partition or delete user files.
D: from the first Windows may appear as C: when you boot into the second Windows. This is normal.
bcdboot, bcdedit, msconfig, and WinRE are usually enough. Third-party tools may be convenient, but they are not required for the procedure described here.
To add a second Windows installation to the boot menu, first identify the correct drive letter of the second Windows folder. In most cases, the safest command is bcdboot D:\Windows /d /addlast from an elevated Command Prompt in the Windows installation that already starts.
If you are working from recovery mode or after disk cloning, mount the EFI System Partition and use bcdboot D:\Windows /s S: /f UEFI /d /addlast. After the entry appears, rename both menu items, set a reasonable timeout, and restart several times before deleting any old partitions or boot entries.