Windows 10 drive rendered inoperable during OSX 10.15.4 Upgrade

[Big-W]

Your Windows EFI folder is missing, this is what output should look like;

 

[Going Bald]

cheers..here we go..

OSX is on an internal nVme drive
Windows is on an SSD SATA drive

And I see your problem - Windows is installed in Legacy Mode.
If you boot to the Clover screen and right tab over to exit Clover will it boot Windows?

 

[RuC2020]

And I see your problem - Windows is installed in Legacy Mode.
If you boot to the Clover screen and right tab over to exit Clover will it boot Windows?

No..it seems if I select the 'Exit Clover' option, I get the "Reboot and select proper boot device or Insert Boot Media in selected Boot device and press a key" screen pop up (screen grab attached).

 

[RuC2020]

Your Windows EFI folder is missing, this is what output should look like;View attachment 458399

ah ha ! So did this get wiped somehow? As windows has been previously been booting fine along with OSX for a month or so, did I wipe the 'Windows EFI Folder' though user error? I just ran Multibeast clicked on a few of the options...& is there an *easy* fix that a beginner can follow? I did start on that last 6 page thread but got very lost..

 

[Going Bald]

ah ha ! So did this get wiped somehow? As windows has been previously been booting fine along with OSX for a month or so, did I wipe the 'Windows EFI Folder' though user error? I just ran Multibeast clicked on a few of the options...& is there an *easy* fix that a beginner can follow? I did start on that last 6 page thread but got very lost..

You never had an EFI partition. If you had there would have been an option for UEFI SATA4 to boot your Win10 in UEF mode in your boot device pick list. When you installed Clover in UEFI to the Mac OS drive you are forcing your system to boot into UEFI Mode. You cannot boot a Legacy drive from UEFI. Can you boot from the USB and still boot Win10?

Suggest you grab another SSD and install Win10 in UEFI Mode. You can then boot it and transfer any filse from the old drive you want to keep. It is a PITA, but you will also have to install any third party software like your AV/Malware and Office software.

 

[RuC2020]

You never had an EFI partition. If you had there would have been an option for UEFI SATA4 to boot your Win10 in UEF mode in your boot device pick list. When you installed Clover in UEFI to the Mac OS drive you are forcing your system to boot into UEFI Mode. You cannot boot a Legacy drive from UEFI. Can you boot from the USB and still boot Win10?

Suggest you grab another SSD and install Win10 in UEFI Mode. You can then boot it and transfer any filse from the old drive you want to keep. It is a PITA, but you will also have to install any third party software like your AV/Malware and Office software.

Ah I see ! It's becoming clearer. Thank you !

Is it safe to try & boot windows via my Clover USB stick without having to remove my OSX nVME drive? Its bit fiddly that's all due to cramming in Dual Graphics cards.

I can try that straight away if so.

 

[Going Bald]

Ah I see ! It's becoming clearer. Thank you !

Is it safe to try & boot windows via my Clover USB stick without having to remove my OSX nVME drive? Its bit fiddly that's all due to cramming in Dual Graphics cards.

I can try that straight away if so.

Yes. There should be no problem

 

[Going Bald]

If it does not work, check BIOS/UEFI for Mode setting CSM enabled or not. Must be enabled to boot Legacy drives.

 

[RuC2020]

If it does not work, check BIOS/UEFI for Mode setting CSM enabled or not. Must be enabled to boot Legacy drives.

OK, no that didn't work.....just got a very brief flash of a windows logo in the middle of the screen....then a blinking cursor top left (reminded of my old ZX81 from the early 80's !)

..ok diving into the BIOS

 

[RuC2020]

Ok, have been poking around the BIOS for the best part of an hour & still no Joy getting windows to boot again (although at least nothing I change seems stop OSX booting which is great)

My Motherboard (MSI z270 SLI Plus) doesn't seem to have any obvious 'CSM on/off' setting, but does have 'Legacy+UEFI' boot mode select. This is always been on. There is also a dedicated 'Windows 8.1/10" switch...this is usually off, but when its 'on' I can only use UEFI boot mode..I have tried every combination of these & still no joy from Windows. Sometime though I get a tiny square windows logo stuck at the centre of the screen....sometimes the flashing cursor....
..ive also tried booting via the Clover USB with these settings & it makes no difference

..the mystery to me is why Windows10 has been booting ok these last few months...any more thoughts ? & if I *do* have to just wipe it & reinstall Win10, I don't remember the install USB stick ever giving me a choice of installing a 'EFI Partition'...it just asked if I wanted to install or not...are there deeper options?