Thanks again topgundcp. This solved the problem.
To verify how well Macrium Rescue performs I tried fixing the boot immediately after backing up? It worked.

Thanks, this will keep the PC busy over the Danish night.
Hopefully I can report a status my morning.

I attach the output from diskpart copy/paste into notepad.
No GPT asterisk

184751

topgundcp
Can you advice how to make screenshots under the Win10 recovery disk?

Yes I do have an external harddisk - it is used for backup (copy paste of all the files on , but about 500 GB free...

Windows 10: Partition 2 Logical 435 GB 2051 MB
Linux Mint: Partition 5 Logical 9 GB 437 GB
Linux Mint Swap: Partition 6 Logical 4501 MB 446 GB

Partition 5 was made in Windows for installing...

Thanks Samuria - currently my only working boot systems are Linux Mint Live USB and Win10 recovery USB - I assume you mean Macrium Reflect Free Macrium Reflect Free - Free download and software...

I have tried to install Linux Mint, and was warned about installing due to an UEFI conflict. I ignored this warning(!).

After that I have been unable to boot from the harddisk - no Win10 boot no...