Sometimes GRUB may be lost due to a fresh Windows install or some other reason. Below is a quick step guide to restore GRUB.
Step 1: Boot your system with a Linux live CD
Step 2: Open a terminal and run the following command to get in to the GRUB command mode:
Step 3: Now to find the partition that has the GRUB boot loader run:
Step 4: From step 3 we will know the partition that has grub boot loader.
replace # with the partition returned by step 3.
Step 5: Run the following command to install grub on the MBR(Master Boot Record) of the first drive.
If you want to install it into the boot sector of a partition instead of MBR run the following command:
replace # with partition
Step 6: To quit the grub command line mode run:
Now reboot the system to find GRUB restored.