I was also looking for a clean, sure way to remove grub, and am sorry to see no solution was offered.

I have tried several times to install Knoppix on a hard drive that had another Linux distro previously installed on it, and grub is never overwritten by the new by “knoppix-installer”. This wouldn't be too bad if the original grub installation was usable for booting Knoppix, but no chance – grub persistent, prevents Knoppix from booting, but doesn't function as a boot loader.

So, I'd like to ask the question again, somewhat modified, though: can anyone explain how to use Knoppix from a live CD to delete a grub installation from a hard derive?

Thanks.