This tutorial will illustrate how to restore grub old settings just in case that you have messed up your linux box trying to install another OS as a dual-os.

Steps:

1. Open “Terminal“
2. type “sudo grub“
3. type “find /boot/grub/stage1“
4. a list of hard drives will appear, now pick the one that is going to provide the grub files.  In my case i am going to pick “hd0” because that is my hard drive.  in this tutorial please replace the 0 for the number of your hard drive given.
5. type “root (hd0,0)“
6. type “setup (hd0)“
7. lastly “quit“

this should take care of grub to be store in the mbr.