How do I restore w10 bootloader? dual boot with ubuntu on separate hdd

So I am looking to REMOVE ubuntu, but right now, my system uses Grub to boot into windows or ubuntu.

Ubuntu is installed on a hdd, w10 installed on a ssd. I BELIEVE that they are both efi installs (cannot remember which way I did it) because both disks are GPT format. On the other hand, if I select UEFI only for boot options in my bios, only "ubuntu" boot device is available on the F12 screen.

I've tried the w10 repair usb, it was not able to auto repair it, I've also tried:
bootrec /FixMbr
bootrec /FixBoot
bootrec /ScanOs
bootrec /RebuildBcd

And the scanOS returns with "0 windows installations found" and rebuildBCD fails bc of this.

I've also tried easyBCD and clicked "write MBR" but all it did was create duplicate "ubuntu" boot devices in the f12 screen.

The only way my ssd shows up as a boot device is if I have legacy mode on in the bios, then it shows up as: "P0 samsung 840..." and fails to boot into windows, can't remember the error code but I've seen it a lot for this issue on forums.

I have two other threads started on r/ubuntu and r/techsupport I've also attached an image below of my disk manager in w10 if it's of any help:

I have unplugged that drive and the "ubuntu" boot device is still the only one that will show up. When I try to boot from that, it brings up a black screen with white text saying something about limited input to grub. And that's as far as I can get.

I will try your suggestion tonight and see if it works.

Side note, I'm looking to do a VFIO passthrough in linux. Basically I will install linux then create a VM within that and run win10 on that which I will use for playing games. my question to you is, if I were to resolve the problem at hand and create a system image of that ssd that has only windows on it, could I wipe that ssd in the future if need be and restore my windows 10 state with that sys image, with all documents and programs, and bootloader intact?

Avocado said:

bcdboot <source> (Specifies the location of the Windows directory to use as the source for copying boot files.)

Will this still work even though when I run bootsec /scanOS the cmd prompt says "0 windows installations detected" ?

More info:

bootrec /fixmbr (writes a MBR to the system partition but does not overwrite the existing partition table)
bootrec /fixboot (writes a new boot sector to the system partition)

Note that bootrec /fixmbr and bootrec /fixboot commands are not needed at all, if the hard drive has a GPT partition style. UEFI mode do not use boot sectors on the hard drive and do not require active partition to be set.

bootrec /rebuildbcd

The bootrec /rebuildbcd command will search for Windows installations not included in the Boot Configuration Data (BCD) and then ask you if you'd like to add one or more to it.

BCDBoot Command-Line Options

"Repair the system partition. If the system partition has been corrupted, you can use BCDBoot to recreate the system partition files by using new copies of these files from the Windows partition."

Thank you very much Avodcado. I will try all of this tonight after work.

Avocado said:

Type in:

diskpart
list disk
select disk 0 #(zero) Yours maybe different
list volume #look for the EFI SYSTEM partition FAT32 hidden usually 100MB (mine is Volume 3)
select volume 3 #whatever number yours is, maybe different change accordingly
format fs=fat32 quick label=System
list volume #look to see which Volume is Windows (mine is drive C) Remember it!
exit

At the command prompt type in bcdboot C:\Windows #Where your Windows drive was.

Type exit again.

Click on Turn off computer, remove USB and restart.

Did this and after the bcdboot command I got "failure when attempting to copy boot files"

Computer wouldn't boot after cloning to SSD

See the above thread. I'm thinking you don't have the partition type for what you think is the EFI System Partition set correctly. Under partition type or volume info you should see listed as System, not Hidden:

My EFI System Partition is Volume #4 which is Partition #2 on my Drive #0:

Code:

Microsoft Windows [Version 10.0.14393]
(c) 2016 Microsoft Corporation. All rights reserved.

C:\windows\system32>diskpart

Microsoft DiskPart version 10.0.14393.0

Copyright (C) 1999-2013 Microsoft Corporation.
On computer: MAIN-DESKTOP

DISKPART> select disk 0

Disk 0 is now the selected disk.

DISKPART> list volume

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 0     E                       DVD-ROM         0 B  No Media
  Volume 1     F                       DVD-ROM         0 B  No Media
  Volume 2     C   WIN10PRO     NTFS   Partition    111 GB  Healthy    Boot
  Volume 3         Recovery     NTFS   Partition    450 MB  Healthy    Hidden
  Volume 4                      FAT32  Partition    100 MB  Healthy    System
  Volume 5     D   Storage      NTFS   Partition    926 GB  Healthy
  Volume 6         RECOVERY     FAT32  Partition   5128 MB  Healthy

DISKPART> list part

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    Recovery           450 MB  1024 KB
  Partition 2    System             100 MB   451 MB
  Partition 3    Reserved            16 MB   551 MB
  Partition 4    Primary            111 GB   567 MB

DISKPART>

Did as instructed in that link. When I boot up it shows a black screen with "reboot and select proper boot device or insert boost media in selected boot device and press a key

Any ideas?