How to Restore Windows 10 from EFI system backup to a BIOS only system?

Question

I have a backup of my System's partitions that I want to restore to a machine, this destination system doesn't support UEFI mode, in which WIndows 10 was first installed.

My Windows 10 system booted from the EFI system partition, where the BCD datastore is located, how should I convert it to a classical System reserved partition?

I see many documents on how to go from BIOS to EFI, but not any from the reverse procedure.

I unfortunately do not have the possibility to enable UEFI mode on the destination hardware.

I'm trying to restore my Windows 10 machine that I have a backup of the image of on a completely different machine, a KVM based virtual machine to be precise.

I'm not asking on how to change the hardware settings on KVM but how to convert an ESP partition that is restored alongside my C: partition to a standard System served one that could boot on legacy harware presented by KVM to the OS.

The VirtIO drivers are already installed in the OS if this info is needed.

References I've looked at:

https://msdn.microsoft.com/fr-fr/library/windows/hardware/dn898504(v=vs.85).aspx https://msdn.microsoft.com/fr-fr/library/windows/hardware/dn898510(v=vs.85).aspx

And of course my previous question where the answer is unfortunately not working anymore since update 1607 of Windows 10. boot windows installed with UEFI on bios only host

What I tried :

1. Restore only the first partition on a MBR disk
2. Set that partition as active

3. Regenerate boot bcd files with BCD as @snayob explained

   PS C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\BCDBoot> .\bootsect.exe /nt60 F: /mbr Target volumes will be updated with BOOTMGR compatible bootcode.

   F: (\?\Volume{833d781b-d99f-11e6-80ec-8223a3a1c06a})

   Successfully updated NTFS filesystem bootcode.
   

   \??\PhysicalDrive3

   Successfully updated disk bootcode.
   

   Bootcode was successfully updated on all targeted volumes. PS C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\DISM> cd "C:\Program Files (x86)\Windows Kits\10\Assessment and Deployment Kit\Deployment Tools\amd64\BCDBoot" .\bcdboot.exe F:\Windows /s F: /v /f BIOS BFSVC: ServiceBootFiles MuiOnly:n Res:y Fonts:y BootMgrOvw:nBootStatOvw:n DbgTransports:y CreateSetupObj :n .\bcdboot.exe : BFSVC Error: Failed to open file F:\Windows\boot\Resources\BOOTRES.DLL for read! Error code = 0x780 At line:2 char:1

   • .\bcdboot.exe F:\Windows /s F: /v /f BIOS
   • ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     • CategoryInfo : NotSpecified: (BFSVC Error: Fa...or code = 0x780:String) [], RemoteExcept ion
     • FullyQualifiedErrorId : NativeCommandError

   BFSVC Warning: Failed to determine source OS version. BFSVC Error: Failed to open file F:\Windows\boot\PCAT\bootmgr for read! Error code = 0x780 BFSVC Error: Failed to validate boot manager checksum (F:\Windows\boot\PCAT\bootmgr)! Error code = 0xc1 Failure when attempting to copy boot files.

Answer 1

Windows 10 adapts pretty well on hardware change.

For example you can use the same Windows 10 VHD installation on native computer and in Hyper-V.

So you need just to copy your Windows 10 partition - only partition where \windows folder is placed.

1. Make destination disk MBR style, create only one single partition, make partition active, map it to any drive letter say Z: (it will be future c: drive)

2. Copy Windows partition from backup to destination disk (single partition) eventually on file by file basis (depends on software used for making backup).

Then write MBR and PBR using bootsect.exe

3. bootsect /nt60 Z: /mbr

Then write boot files using bcdboot.exe

4. bcdboot Z:\windows /s Z: