GRUB not showing up after changing grub theme! HELP

Hi,
I am running zorin os 9 ultimate x64 in my dell inspiron 1440 laptop (with broken screen). Today I first installed burg, then uninstalled burg & then changed the theme of my grub2 using grub-customizer. But the grub doesn't show up when I booted. So I had to boot into Windows 7 recovery tools and then install the Windows bootloader again, so I could at-least boot into my dual-boot windows. But I want my Zorin back. Its not a black screen, but my external monitor says 'no signal'.
With the default grub (with that zorin honeycomb & blue background) too, I couldnt see the grub. But somehow I booted into zorin and then updated the grub config file at etc/default (to disable LVDS and force the VGA output at 1024x768 reolution, and also added the command:

Code:

GRUB_GFXMODE=1024x768

, and then the default grub came up. But now after changing theme, and again setting the same settings (i.e. disable the LVDS, force VGA output at 1024x768), and now it doesnt boot.

So please help me in getting my bootloader back. I also have a live cd of the same.
But I cannot run the

Code:

sudo update-grub

command from the live cd, (I have chrooted into the drive)

Hi,

boot into recovery mode and activate "Network" (cable connection required) then drop to "root" and type

Code:

sudo update-grub

See if that works!.