antix 13 uses grub-legacy. antix 15 uses grub2. there is no option at install for grub-legacy, however, if you have grub-legacy installed you can choose in the antiX installer to NOT install grub at all (or to install a second grub bootloader in the root partition instead of the mbr, handy for chainloading). then you could point your existing grub-legacy boot loader at your new antiX installation.