First, be sure that you've actually plugged an EFI-bootable USB flash drive into the computer. The option may not be present if there's no USB flash drive inserted or if it's not bootable in EFI mode.
If you've done that, I recommend you try another image for diagnostic purposes. Another distribution should work fine if you've got it handy. If you want something quick to download, there's a USB flash drive image of my rEFInd boot manager that you can download and prepare quickly for testing purposes.
Another thing to try is another physical medium. I've seen a few reports of USB flash drives that work fine in an OS but that firmware doesn't seem to like. I'm not sure of the cause of the problem, but if this is what you're running into, a new USB flash drive might fix it.
You could try using rEFInd to work around the problem. Install it on your hard disk from Windows (see the rEFInd documentation for instructions), or use it on another USB flash drive. When you boot to rEFInd with a bootable USB flash drive plugged in, it should give you an option to boot it. This might work around EFI bugs, but probably not hardware incompatibility.
Speaking of EFI bugs, you might try upgrading your firmware.
Finally, you could try setting up a partition with the Ubuntu installation files on it and use rEFInd to boot the installer from there. In theory this should work, but there may well be some "gotchas," and I don't have detailed step-by-step instructions.
Try these in whatever order you like; I don't mean to imply anything by their ordering (except for the first item, which is the most basic one).
Start a Ubuntu Linux (14.04) Live CD in UEFI mode. In case of a USB boot device, disable "Fast Boot" in UEFI.
Open a terminal window (Ctrl+Alt+T)
To verify that you are actually running in UEFI mode, use this bash command:
$ [ -d /sys/firmware/efi ] && echo UEFI || echo BIOS
The resulting output should be:
UEFI
In case it says BIOS, reboot into your firmware and correct the boot device preference.
To do the BIOS to EFI/UEFI conversion enter these commands:
$ sudo mount /dev/sda1 /mnt
$ sudo mkdir -p /mnt/boot/efi
$ sudo mount /dev/sda3 /mnt/boot/efi
$ sudo mount --bind /dev /mnt/dev
$ sudo mount --bind /proc /mnt/proc
$ sudo mount --bind /sys /mnt/sys
$ sudo mount --bind /run /mnt/run
$ modprobe efivars
$ sudo chroot /mnt
# apt-get install grub-efi-amd64
Apt-get networking failure?
# rm /etc/resolv.conf
# ln -s ../run/systemd/resolve/stub-resolv.conf resolv.conf
# apt-get install grub-efi-amd64
No apt-get failure
The following extra packages will be installed:
efibootmgr grub-efi-amd64-bin
The following packages will be removed:
grub-gfxpayload-lists grub-pc
...
After this operation, 2,399 kB of additional disk space will be used.
# grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu --recheck --no-floppy --debug
Despite ending in error message:
Fatal: Couldn't open either sysfs or procfs directories for accessing EFI variables.
Try 'modprobe efivars' as root.
the next reboot already shows "ubuntu" in the firmware its boot options menu, and boots to the console as before, except for now booting in efi mode:
$ dmesg | grep EFI
efi: EFI v2.31 by American Megatrends
fb0: EFI VGA frame buffer device
EFI Variables Facility v0.08 2004-May-17
fb: switching to inteldrmfb from EFI VGA
In case something goes wrong, https://superuser.com/questions/376470/how-to-reinstall-grub2-efi might help.
Best Answer
You can do this easily using Visual BCD Editor in Windows 7/8/10.
Map EFI System drive to Z: using
mountvol z: /s
Run Visual BCD Editor and select "Store","Backup store".
a)Click on browse icon in dialog and using the explorer window select z: drive - now you have full access to EFI System Partition (ESP).
b)Click on EFI folder to expand - you will see "Boot", "Microsoft" and "ubuntu" folders if you have Windows and Ubuntu installed.
c) You can delete "ubuntu" directory by selecting it and pressing "Del" key.
After reboot Ubuntu boot option in UEFI boot menu will be completely gone.
Note:
You could alternatively use bcdedit.exe to delete EFI boot entry for Ubuntu and use command prompt to delete "ubuntu" folder from EFI System Partition (drive z:) if you feel more comfortable with commands.