This is on a dual boot system with Win7 and Ubuntu 19.10. It is a BIOS system.
After a Windows update last week I couldn't boot into Windows anymore. The boot halted with error 0xc0000428 for /Windows/system32/winload.exe "Windows cannot verify the digital signature for this file". I still could boot Windows in recovery mode, though.
After some research I booted Windows in repair mode, dropped to the command line and used
After doing that Windows 7 booted correctly, but Grub was gone.
Then I used a Rescatux USB stick to restore Grub. It worked but now Windows throws the same winload file signature error as in the beginning.
I'm stuck, please help.