My situation is the same that is addressed here
I tried to install Ubuntu 12.04 from the Live CD alongside my current Windows 7. I have to switch my BIOS to legacy mode in order to boot from CD. If I were to do a normal installation and remain in legacy mode, the BIOS will display "operating system not found". If I switch back then the BIOS just boots to windows.
To solve the problem, I tried following the steps in the previous two articles. My drive is partitioned as:
sda1 FAT32 Location of Windows EFI files (flagged as boot in Ubuntu install)
sda3 NFTS Windows
sda4 ext4 Ubuntu root
sda6 ext4 Ubuntu home
I was a little confused by the requirement in the second article to "be careful to install Grub bootloader in /dev/sda3"
In my case, the relevant partition is sda1. I have tried three things: setting the sda1 mount point as
/boot/efi, and as the special reserved grub partition. In each install I indicated that grub should be installed in sda1.
After each install I reboot to the live CD and look in the sda1. I see EFI/Boot and EFI/Windows, but no EFI/Ubuntu and consequently no grubx64.efi.
I understand the recommended procedure of moving grubx64.efi into the EFI/Boot directory and replacing the present bootx64.efi file, but I see no grubx64.efi and I don't know where it should be.