It uses EFI instead of BIOS (it's generally the same of course) so you can't use gfxgrub which is used in Mint from Celena (or Cassandra - my memory is short
)Download supergrub (google for it) only about 4 MB and burn it to a CD and use it to install a standard grub.
You can read more here
http://www.linuxmint.com/forum/viewtopi ... cbook+grub
Very informative