This question already has an answer here:
I have a laptop ASUS, model G551J, with ubuntu 14.04.5 installed (64-bit architecture). After running on it a USB live of Lubuntu, 32-bit, the laptop won't boot any more. A grub-rescue prompt turns up with the following error:
error:file '/boot/grub/i386-pc/normal.mod' not found.
I ran a USB live of ubuntu 14.04.5, and executed boot-repair, but it threw an error, with this log:
There is a very similar question with a very good answer here:
But this question is more about why boot-repair failed to repair this issue.
How can I fix this problem?