merge 2 single working disks - one has Win-XP (SvP3+) the other Win-7 (SP2)

[snahL]

I've got 2 SSDs that I'd like merge onto one SSD.

Both SSDs boot their OS  properly by changing the Boot Device Priority in BIOS.

On both SSDs I reduced the partition size enough so they can both reside on the destination SSD.

Then I created partition-images from both SSDs.

The partition image from SSD1 (Win7) got restored onto SSD2 (Win XP) into its separate partition.

and vice versa

the partition image from SSD2 (Win XP) got restored onto SSD1 (Win7) into its separate partition.

Screenshot current Disk Management taken on SSD2 (Win XP)

These two versions to be merged are my starting point.

On SSD1 (Win7) I installed "Visual BCD Editor" and on SSD2 (Win XP) "Dual-boot Repair 10" respectively.

... and from here on I am lost on how to obtain a proper dual-boot system.

additional limitations I am facing:

Unfortunately I don't have a DVD-player for that system. 

Even though I can boot from an USB-stick, for some reason, I am not able to use USB-Stick containing Win7-Install media (same USB-stick works fine on other systems). 

It's an old system that won't accept a Win10 installation.

Would be nice I someone can help me achieve my goal, thanks.

[boyans.net]

What tool do you use to backup/restore image of OS?

You cannot simply make copy of OS to another partition as some important OS paths are stored in registry!

[snahL]

The are several tools I have been using. 

To me EaseUS is quite convenient for Windows. 

GParted is also great. I have been using GParted running off a bootable CD and recently more often on a Raspberry Pi running Strech to manipulate HDDs formatted with NTFS. 

I am aware copying partitions sector by sector is normally successful.

The question of my post boils down to is:

How to move/copy a Windows OS partition from one disk to another partition on another disk so that the OS remains functional.

A fresh install of the OS onto any other partition normally works fine, so a move/copy should also be possible. 

I'd assume a decisive factor is to make the copied OS 'understand' the required descriptors (which are not clearly visible without special knowledge and tools).

For example in windows 10 the registry key 

{HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices}

contains the binary address data for the Windows boot drive C
{\DosDevices\C:}

its binary address data translate to a GUID used throughout the entries of a specific windows registry

{#{18e8b7ea-a655-11e5-8d7f-002683152180}}

I have no idea whether this binary address data IS actually pointing to a physical location on partition of a disk.

[snahL]

Nobody?

Is it that my attempt is not possible?

[boyans.net]

Hi,

Sorry for the delay.

You are completely right - the place to look is {HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices}

and then {\DosDevices\C:} {\DosDevices\D:} .......

The information stored for MBR disk = diskID(4bytes) + offset

                                              GPT disk = diskID(8bytes) + partitionID

The same information is stored in the BCD store as deviceID for the corresponding loader.

Tools that backup and restore partitions should adjust information stored for {\DosDevices\C:} 

if restoring to different disk and partition. 

I think popular tools should cope with this task as source partition is known at backup time 

and destination partition is known at restore time. 

bcdboot command can create a loader for visible/mapped partitions and it will be the default loader.

See https://www.boyans.net/RepairWindows/RepairWindowsBCD.html for bcdboot options.