step to install grub using the Live CD.

1. The first step using a live CD and open the terminal.

2. Log in to the GRUB menu:
$ sudo grub or  grub

grub> geometry (hd1);

command to find the Linux active partition  .

example in the linux partition the second partition.
grub> root (hd0, 2);

3. Wait for the process is complete and then reboot the computer.

Note : be caution before doing above steps