I've tried to fix GRUB using Boot Repair. This is the ticket I got.
When the computer starts Windows 7 is launched without any GRUB message. I don't really know what else to do. Any help would be really appreciated.
I see you have chosen to install
So you need to install
Re run the
More information is available in How to boot Ubuntu from EFI/UEFI?.
Let us know how it went.