Error 5: Partition table invallid or corrupt

After many experimentations with different systems my Intel Mac Mini, Intel 945, core 2 Duo, gives the message as in the Title above when installing Linux to external firewire-drive.
Where can I find clear and good help how to repair MBR?
(There is Apple “Times Machine” backup partition HFS+ in Firewire disk.))

That doesn’t look like MBR. It appears that your boot loader program doesn’t understand the disk format.

Are you using GRUB when you ought use lilo or something? Sorry I don’t know the Mac hardware so I haven’t booted off ext firewire drive.

I use Grub. Should I change to Lilo?