I recently installed linux mint. It did not give me the option of installing grub or not and installed its own version / config into the mbr.
To get back to square one
Log into the Linux OS you want to have the grub mastered on and as root run grub-install /dev/sda (this might change depending upon the location of you MBR)
If you are reading this and stating; how can I do this if I can not log into my Linux OS; use a live disc, map / swap and as root run grub-install