GRUB installation from BOSS Live CD/DVD

Boot the DVD and select the option live

open terminal

give the command as follows:
Note: mountedpartition is the partion, where OS is installed for eg: It might have mounted on /media/XXXXXXXXXXX/

Step I
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#mount --bind /dev /mountedpartition/dev
#mount --bind /sys /mountedpartition/sys
#mount --bind /proc /mountedpartition/proc
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Step II

#chroot /mountedpartition/
#grub-install /dev/sda
#exit

Finally restart your system.