You must be root in order to write to the MBR.

Delete all of the partitions and start fresh. Unless you wish to keep that utility partition. There should be no issues using a partition editor, but, you can always zero out the MBR with the command: dd if=/dev/zero of=/dev/your_hard_drive bs=512 count=1 . This will write 512 zeroes to the first sector of your designated device.

If you wish to keep a copy of the MBR, use the command: dd if=/dev/your_hard_drive of=/file/name bs=512 count=1 .