dual boot 2x windows10 on UEFI/GPT

witty

New Member
As I am quite used to dual/multiple boot-options (boot-managers etc) in BIOS/MBR environment, but not in UEFI/GPT, I wonder if and how the following can work:
I copied (cloned) my windows-system partition(A) on my HDD to a second partition(B). Now I want to "simply" boot either (A) or (B), while the "inactive" windows-partition being hidden.

Any help highly appreciated!
 

Terry60

Knows where his towel is.
Staff member
There is no capacity in the Windows bootmgr to alter the hidden status of a drive, though it does respect the hide bit if present.
A practical solution - Add a BCD entry (Adding Entries) for your cloned OS, pointing to the drive letter as seen by the running OS.
Boot the OS to ensure that your clone actually works. From that OS, use Device Management to remove the letter for the partition containing your main OS.
Reboot into the Main OS and remove the letter for the cloned copy.
You should now have a working dual-boot in which both systems run without "seeing" the other.
Explorer does not display any drive without a disk letter.
If Explorer can't "see" it, you can't access it, hence the systems are mutually hidden without troubling the "hide" bit.

I personally wouldn't bother. I like to be able to access my old W7 from W10 occasionally.
I can see the point however if your PC is a multi-user asset and you don't want third parties getting confused.
 

witty

New Member
Terry, thanks for this easy/straight forward approach!

When I boot into my 2nd Win10, I get a black screen only showing the mouse-pointer...
BUT as team-viewer is installed, I am able to connect with team-viewer (so network and some services ARE running).
Booting in safe-mode shows the login-screen, but after submitting the password, I receive "sihost.exe unkown hard error".

Any idea?
 

Terry60

Knows where his towel is.
Staff member
It all depends on how you "cloned" the OS (and indeed if it is actually a true clone or a modified copy)
Partition Managers have multiple commands to "copy" one partition to another, some are only suitable for data partitions, some are specifically for an OS, and in that latter category there are many different approaches.
Some PMs will truly clone a partition, i.e. make a faithful bit for bit copy and this has potential problems if the partition in question contains a BCD, because the BCD addresses partitions by pointing to the offset on a unique device signature, which of course will be pointing to the original copy, not the clone. That's easily repaired however so not a show stopper.
Some PMs will call the copy a clone, but will actually make thousands of registry edits to effect a disk letter change of the copied OS.
My advice is to read the small print of the particular PM you used with reference to the exact mechanism of the individual "copy" command you chose.
One approach which should work regardless of the architecture of the PM you used is to make use of the Backup and Restore commands if the copy isn't doing what you expected. A Backup of the OS, but restored to a different place should give you a working second OS which can be dual booted with EasyBCD.
 
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