This is my situation:
I had in my hard drive two operating systems: Windows 8.1 and Ubuntu 12.04 LTS Precise Pangolin.
Using a bootable USB stick, I created another partition to install in it the newer Ubuntu MATE 16.04 LTS Xenial Xerus (the operating system in the bootable USB stick).
After creating the partition and trying to install Ubuntu MATE 16.04 LTS Xenial Xerus in it, I got some error messages that I cant remember right now. The result was that I couldn`t boot my computer anymore and, when booting my machine, I was sent to a black screen with the words "grub rescue" on it.
Then, I decided to completely erase my entire hard disk and install Ubuntu 12.04 LTS Precise Pangoling in it once again. I used a bootable USB stick with Precise in it and used the entire hard disk in the install.
The install was running smooth and by the numbers until I got this message in the end:
grub-efi-amd64-signed failed to install into /target/. Without GRUB boot loader, the installed system will not boot
I ran boot repair and got no solutions at all. Only a black screen with the words grub rescue on it.
My hard disk partitions are this way right now:
Partition File-System Size Used Unused Flags
/dev/sda1 fat-32 94.00-MiB 1.46-MiB 92.54-MiB boot
/dev/sda2 ext4 927.48-MiB 17.75-GiB 909.73-GiB
/dev/sda3 (key image) linux-swap 3.94-GiB
StackOverflow doesn`t support tables. Sorry for the mess above.
Some additional informations:
I think something went wrong when trying to configure UEFI, Secure Boot, Fast Boot and all those stuffs of "modern" computer systems. The BIOS was so easy to use. The fact is that I did something wrong, since my computer is a useless pile of metal right now. I cant boot it and I cant install anything in it.
By the way, all I want right now is to install Ubuntu 12.04 LTS Precise Pangoling in my computer. I have a bootable USB stick with it and I don`t mind using the entire hard disk for that.