I had a dual-boot setup of Ubuntu 13.10 and Windows 8 on my Asus Vivobook. Initially the dual-boot setup asked for some tweaking as Windows 8 insisted on being UEFI started. But it worked lateron.
This morning, I was silly to accept the proposed upgrade to Windows 8.1. Now windows has replaced the boot manager and I no longer get asked if I want to boot to Ubuntu. The computer boots straight to Windows.
As I really require both OS's, I have been trying to create a functional dual boot situation. I partly succeeded, but for the time being, I am stuck in a situation where the Grub options are shown, and only Ubuntu can be started.
Whenever I try any of the Windows booting methods provided in the grub menu, I get a nice blue screen with the message:
Your PC needs to be repaired Error code 0xc0000225
After Return, next nice blue screen says:
File:<Windows<system32<winload.efi is missing with same error code.
I have CSM enabled in BIOS, as well as "secure boot" option.
So, how do I reinstate dualboot after upgrading to Windows 8.1?