I think you describe here very closely just what I tried to do today but could not boot as hoped at the end
I hope it's close enough to the OP that it will help others in similar situations
PLAN: Speed up system startup and Windows maintenance by Moving ONLY C: drive from slow HDD 1TB
to new smaller SSD (120GB - big enough for my windows, but not for any user DATA)
User data all in new D: drive, located on HDD
Starting System is a single disk GPT UEFI system, running Win 10 Home
OBJECTIVE is a 2 disk system; C: on SSD with all OS and software; all Userdata in new D: drive located on HDD
PREPARATION: Create new D: drive on HDD and move Location of all user data to D:\Users\Name\Docs, Pics etc
Shrink C: to 100 GB, so it will fit on 120GB SSD
Take full macrium backup of HDD
Disconnect HDD and install New Win 10 on SSD;
a 100% default Win 10 install; Small size (no data); 2 system partitions + C: about 110GB
It booted OK of course
The HDD was disconnected during this install and reboot
Power off: reconnected HDD; both SSD & HDD to have power on next reboot
Enabled legacy boot to permit Boot to CD
Booted to Macrium Rescue and restored HDD C: partition (100GB) into SDD C: partition just created
(I definitely got the source and target correct)
At this point C: drive on SSD is a clone of C: drive on HDD)
The resulting C: on SSD now expects an available D: drive in another partition, (of which one instance is located on HDD.
I think this may be where I now go wrong...
Before exiting the Rescue environment, I used Macrium to fix the boot partitions.
choosing both EFI and Windows on SSD. Fix Boot had detected two installations as expected
The system booted OK, but it booted into Windows on HDD
, not SSD
and I couldn't make it boot into the SSD copy of Windows
I've an idea maybe I should have installed Win 10 on the empty SSD with the HDD still connected
Where did I go wrong???
I never did fully understand UEFI boot & the use of GPT disks.
Perhaps I will now?
Thank you in anticipation