Solved How can I change system C: drive?

I have a VHDX which I sometimes boot from and sometimes use as a VM in Hyper V. It has Windows installed on the default C: drive.

This is somewhat confusing as the C: may be the original C: drive or the VHDX C: drive (with the original C: drive renamed to H: in my case). I want C: to always be the native boot and T: (for example) to always be the boot for the VHDX.

Can I change the VHDX to have Windows installed to say T:? I was thinking of renaming all instances of C: to T: in the registry and updating BCDEDIT. It is not possible to change system disk in disk management.

If this is not possible can I re-install windows on the VHDX and specify a different letter and C:?

This is how it looks when booting from VHDX:

Hi

Not sure whether helps but i would recommend trying this :

How to restore the system/boot drive letter in Windows

How to Change Windows Drive Letter Using Registry in Xp: 18 Steps

Boot from the VHD and try changing the OS partition's letter to "T".

Thanks - I'll try it and see....

By convention, when you install Windows, the letter C: is reserved for Windows and nothing you can do about it, ,not when the windows is active, disk management/dispart will not allow you to re-assign to any other letter on the current boot/pagefile volume.
Looking at the screen shot, I think you are currently booting from the virtual VHDX and your other Windows partition is re-asigned to H:, This is normal, you can re-assign to any other letter or even remove the drive letter to make it invisible but once you boot from it, its letter will be C: again and your Virtual VHDX will probably re-assigned to be H:. In another word, when you boot the VHDX, it will see your other Windows as another regular drive, and pick one letter available to assign it and vice versa.

I have 2 SSD's, both run Windows and that's how it works. The drive letter assignment is interchangeable, so not to be confused about it, I remove the letter to make it invisible and the same for the other. It'll be better so I don't mess around with the other currently not active.

Decided not to change it in the end.