You don't need to format/reinstall filesystems, because you have bootloader problems! By using the following procedure you can play around with bootloaders with impunity.
Originally Posted by katriel
Boot with the Live CD. Open a terminal of your choice, or console if you prefer.
You can restart after that. Substitute your partitions for sda*.
sudo mount /dev/sda7 /mnt // Assuming sda7 is your / partition of your "sick" Ubuntu system
sudo mount /dev/sda1 /mnt/boot // Assuming sda1 is your /boot partition. Needed only if you have a separate partition for boot!
sudo mount --bind /dev /mnt/dev // Get those pesky sda devices from the live CD
sudo mount -t proc /proc /mnt/proc // Ditto for proc
sudo chroot /mnt // Now you are working from your "sick" Ubuntu
................. // Do what you want in your bootloader for UEFI support
sudo update-grub // if using grub
sudo lilo // if using lilo
exit // Return to Live CD
sudo umount /mnt/boot
sudo umount /mnt/dev
sudo umount /mnt/proc
sudo umount /mnt
This allows you to try different things with your bootloader.
UEFI is difficult and tricky. You need to install special grub
Also checkout thread: http://ubuntuforums.org/showthread.php?t=2125099&page=2
Oldfred is very experience with UEFI as I hear.