How to Remove LILO, GRUB or Master Boot Record from system

A hard disk generally stores the system bootloader’s binary code in the first 512 sectors, or 512 bytes. LILO and GRUB are bootloaders that embed themselves in the master boot record, or MBR, also within the first 512 bytes. Before removing LILO or GRUB, understand the MBR structure so you do not confuse the number of bytes to erase. The MBR structure is shown in the diagram (reference: http://en.wikipedia.org/wiki/Master_boot_record). The diagram shows that partition tables start at address 446. To remove LILO or GRUB, erase no more than 446 bytes, using:

# dd if=/dev/zero of=/dev/ bs=446 count=1

To erase the partition tables too, use:

# dd if=/dev/zero of=/dev/ bs=512 count=1

Warning: Once you erase the MBR, the machine cannot boot.