Windows 10: UEFI dual boot 2x WIN 10 Pro failing

Dear all,
I ll be the first to admit that I have created this mess, but now got so far stuck that I can't find a way out anymore. Any help is very welcome!

What I did:

1. I started with 2 perfectly running win 10 pro installations on 2 different drives ("Work" drive and "Play" drive), with every restart ending up at the WIN 10 UEFI Dual Boot Screen.
2. Then I decided to reinstall the "Play" drive, so I deleted all partitions on this drive and installed WIN 10 Pro through my USB drive created with the Windows Media Creation tool.
3. I now believe that this drive originally contained the Boot sector and had a GTP table.
4. Upon restart I could only boot into the new "Play" drive, which was now in MBR table (MB is set to UEFI + CSM mode).
5. I manged to rebuild the Boot sector on the "Work" drive with bootrec /FixMbr bootrec /FixBoot bootrec /ScanOs bootrec /RebuildBcd. Which allowed me to boot to both drives, but only by going into the boot menu (F12), so no DUAL Boot Screen.
6. Running Diskpart I noticed that now both drives were in MBR. Thinking this might be an issue I converted both to GTP with the win 10 MBR2GTP commands.
7. This didn't change anything either. On restart I didnt get any DUAL Boot screen and could only get to the "Play" drive by going into the Boot menu, or changing the Boot order in the BIOS.

Now the real mess started:

8. I then decided to install EasyBCD on the "Work" drive and added the to bootable drives. This worked ONCE. On restart I got the UEFI Dual boot screen and booted to the "Play" drive.
9. Restarting from the "Play" drive however got me straight back to the "Play" drive and restarting from their did the same without any dual boot screen.
10. Then I thought I ought to install EasyBCD on the "Play" drive as well, which I did.
11. This resulted in No dual boot screen and trying to boot to the "Play" drive I got a No windows installation found
12. Now desperate I ran an auto-repair from Easy Recovery Essentials on the "Play" drive. Upon restart I didn't get any dual boot screen and booting (F12) to the "Play" drive resulted in a BSOD stating, "inaccessible boot device".
13.Checking the "Play" drive in Diskpart showed that Easy Recovery Essentials has converted the "Play" drive back to MBR.
14. ... and that where I am at!!

I feel I should just clean the whole mess up and rebuild the UEFI Boot sectors etc from scratch, but I don't know where to start now.

So in short, I would like to be able to boot from the Win 10 UEFI Dual boot screen, showing both my Win 10 pro "Work" install and my Win10 Pro "Play" install, if that makes sense.

Reinstalling the "Work" drive would only be a last last last resort option.

Thanks!

Maybe the below DISKPart / EasyBCD overview helps:





Disk management etc - Album on Imgur

:)

 

UEFI dual boot 2x WIN 10 Pro failing

Hi Navy,

please see the results below:

 

UEFI dual boot 2x WIN 10 Pro failing

With first disk to boot, I suppose you mean the C: drive with Win Work on it..right?

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UEFI dual boot 2x WIN 10 Pro failing

BIOS is in UEFI mode.. this is what I got by booting to the disk.. doens't look very good





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I managed to boot into the " Play" drive where I am now