Short answer: on UEFI+GPT you don’t use an “active” flag — you need a valid EFI System Partition (ESP, small FAT32 partition) with the Windows boot files (\EFI\Microsoft\Boot... and a UEFI boot entry. Your clone most likely doesn’t have an ESP, or the ESP is present but empty / wrong type / missing boot files. The fix is to either copy/restore the ESP from the source disk or create an ESP and recreate the boot files with bcdboot. Below are safe, step‑by‑step ways to check and fix it.
Important warning
- Don’t delete or repartition anything until you’ve backed up important files or have a full image. If you’re unsure, post the disk/volume listing (instructions below) before deleting.
1) Boot into a rescue environment
- Boot the PC from your Windows install USB or from the Macrium Reflect rescue USB. When booted to the PE environment open a command prompt (Shift+F10 with Windows installer, or “Command Prompt” in Macrium).
2) Identify the disks and volumes (paste these results if you want me to check)
Run:
diskpart
list disk
select disk X (replace X with the disk number of the new NVMe)
list partition
list volume
exit
What to look for:
- A small FAT32 partition ~100–300 MB → that’s the ESP.
- A partition with the Windows files (large NTFS, contains \Windows).
If you do NOT see a FAT32 ESP on the NVMe, continue to step 3. If you see an ESP but it’s empty or lacks the Microsoft folder, skip to step 4.
3) Create an EFI System Partition (if missing)
(Only do this if there is room — creating a 260 MB partition is safe. If your clone used all space you may need to shrink Windows partition slightly first; ask if you need help.
At the command prompt:
diskpart
select disk X
create partition efi size=260
format quick fs=fat32 label=System
assign letter=S
exit
Now you have an ESP mounted as S:.
4) Recreate the boot files with bcdboot
Find which letter Windows is on in the rescue environment:
- Try DIR C:\Windows, D:\Windows, etc., or run diskpart list vol to see which volume is the Windows partition and note its letter (assign a letter if it has none).
Then run (replace letters as needed):
bcdboot C:\Windows /s S: /f UEFI
Expected result: “Boot files successfully created.” This copies \EFI\Microsoft\Boot\bootmgfw.efi and creates the BCD store on the ESP.
If bcdboot errors:
- If Windows is BitLocker encrypted, you must unlock or suspend BitLocker first.
- If you get ACCESS DENIED or similar, check that S: is FAT32 and writable.
5) Remove assigned letter and reboot
(Optional cleanup)
diskpart
select volume <number of S:>
remove letter=S
exit
Reboot, enter UEFI setup and make sure the NVMe’s “Windows Boot Manager” entry is first (sometimes appears as “Windows Boot Manager (your NVMe model)”). If it does not appear, try the UEFI boot menu — the newly created boot entry should show.
Alternative if ESP exists but no boot entry
- If ESP contains \EFI\Microsoft\Boot\bootmgfw.efi but the UEFI entry is missing, you can recreate the entry with efibootmgr (Linux) or use EasyUEFI in Windows, or simply run bcdboot as above — it usually creates the firmware entry.
If cloning didn’t copy the ESP at all
- When you cloned, some cloning tools skip small system partitions by default. If you still have the original drive, the safest is to copy the ESP from the original to the new drive (byte-copy the 100–260 MB FAT32 partition) or recreate it and use bcdboot.
If Macrium “Fix Boot Problems” complains about “active partition”
- That message is generic (older MBR phrasing). On GPT/UEFI the tool still expects a usable ESP. The correct action is creating/restoring the ESP and running bcdboot as above.
If you prefer a GUI method inside Windows
- Boot the cloned disk via the rescue environment, install/run EasyUEFI or use Windows’ Disk Management to check partitions, then use EasyUEFI to add a boot entry pointing to \EFI\Microsoft\Boot\bootmgfw.efi on the ESP.
What I need from you if it still fails
- Paste the output of:
diskpart -> list disk -> select disk X -> list partition -> list volume
- Or a screenshot of Disk Management showing partitions for both the source and the cloned NVMe.
I can then give exact commands (which partition to select, whether it’s safe to delete/recreate the ESP, or steps to copy the ESP).
. Confirm by dir H:\Windows.
