In case anybody is having issues setting up Ubuntu 12.10 in Grub4DOS, I’ve finally got the configuration down. I keep all my .iso files in a /multiboot/ subdirectory, so change your path as needed for your thumb drive. Use the following:
title Ubuntu 12.10 (x64)
find --set-root /multiboot/ubuntu-12.10-desktop-amd64.iso
map --heads=0 --sectors-per-track=0 /multiboot/ubuntu-12.10-desktop-amd64.iso (0xff) || map --mem /multiboot/ubuntu-12.10-desktop-amd64.iso (0xff)
map --hook
root (0xff)
kernel /casper/vmlinuz boot=casper iso-scan/filename=/multiboot/ubuntu-12.10-desktop-amd64.iso quiet splash --
initrd /casper/initrd.lz
