Boot into rescue mode using the Ubuntu CD, mount the root partition and edit the file.
That would get the file edited but he wouldn't be able to run update-grub without doing more work. Its been a while since I had to do this sort of thing but IIRC you have to chroot before running update-grub which is probably more than a beginner wants to do
Anyway, can't he just add the "nomodeset" to the kernel line of the normal gui login and boot that way? Apart from anything else this would check whether this fixes the problem before going any further.
FireGryphon... in that grub menu that you've already found edit the line that's got quiet splash
on it and just add nomodeset
to the end of it. Then boot by pressing F10. This will revert next time you reboot so you've still got to edit the file and run update-grub. To do that:
- open a terminal window
- enter this command gksudo gedit /etc/default/grub
- put nomodeset
in the quotes next to GRUB_CMDLINE_LINUX=
and save the file.
- then use this command sudo update-grub
and make a note if it says anything about errors
Another possibility is that despite the gui being garbled the text terminal is still working... when booted into the garbled gui press CTRL+ALT+F1 and see if you can login that way.
If you can then edit the file with:sudo nano -w /etc/default/grub
(CTRL+o saves the file and CTRL+x closes the text editor)
then run:sudo update-grub
If nomodeset doesn't work then try removing splash
(which causes the pretty splash screen to be shown during bootup as this often causes problems on buggy hardware).