the mbr isn't formatted with any filesystem.
when you install grub, with something like:
root (hd0,0)
setup (hd0)
the 'setup' command tells grub where to install its stage1 image. so, (hd0) just indicates the hard drive as a whole, meaning stage 1 should be installed in the mbr. you could do 'setup (hd0,0)' to have it installed in the first partition, 'setup (hd0,1)' for the second, etc.
when you install grub, with something like:
root (hd0,0)
setup (hd0)
the 'setup' command tells grub where to install its stage1 image. so, (hd0) just indicates the hard drive as a whole, meaning stage 1 should be installed in the mbr. you could do 'setup (hd0,0)' to have it installed in the first partition, 'setup (hd0,1)' for the second, etc.
