I have successfully installed Ubuntu 15.04 alongside Windows 8.1 and everything is great, Grub asks which OS I want to boot to and everything, until I select Windows 8.1 as the OS to boot to.
I'm not saying that Windows no longer works, just the opposite. I can boot to Windows just fine, but when I reboot and want to go to Ubuntu, nothing works. The screen goes blank for about 15 seconds then I get a message stating that a file is missing and gives the file path as
\EFI\ubuntu\shimx64.efi Status: 0xc000007b
I am completely new to Ubuntu.