grub2 - Dual Boot: GRUB disappeared, boot-repair not working and linux partition cannot be accessed

I'm trying to fix a friend's computer. He uses Win7 and ubuntu 14.04 dual boot and ran "secure boot", which seems to have caused major damage: afterwards, GRUB wouldn't show up and the computer booted directly to windows. We tried to reinstall GRUB without success.

Here's what happens:

1. I tried using boot-repair in a LiveSession without success (as nothing changed). I paste the output below.


2. I tried to check hard drives using Gparted, but it gets stuck when searching for disks.


3. I then tried to reinstall GRUB in terminal (following this guide: http://howtoubuntu.org/how-to-repair-restore-reinstall-grub-2-with-a-ubuntu-live-cd), but "sudo mount /dev/sda3 /mnt" wouldn't work as I have to specify the file format, and neither option (ext3, -ext4, -auto) seems to work


4. Finally, the attempt to save the files accessing the ext4 partition from within windows (with ext2read and other programs) also failed, so it seems to me the whole partition is corrupt.

Now here's the output from boot-repair: http://paste.ubuntu.com/8229032

Any ideas? Thanks in advance