GRUB Stage 1.5 is located in the first 30 kilobytes of hard disk immediately following the MBR if this space is not available (Unusual CHS values, GPT or LVM disk) the install of GRUB will fail.
GRUB Stage 1.5 is located in the first 30 kilobytes of hard disk immediately following the MBR and before the first partition. If this space is not available (Unusual partition table, special disk drivers, GPT or LVM disk) the install of Stage 1.5 will fail.