Restore GRUB after Windows install
Boot up into a Live Linux Image.
Mount your old Linux Install, and use chroot to take control of it.
mount /dev/sdc1 /mnt chroot /mnt
You will get grub-probe: error: cannot find a device for / (is /dev mounted?). if you don’t mount you devices, before attempting to install GRUB.
So mount all devices.
mount proc mount sys mount dev
Force GRUB to update it’s configuration file, and re install it back to the MBR.
update-grub grub-install /dev/sdc
When installing GRUB you need to make sure that you don’t specify a number like you did when mounting, otherwise it will be installed on the partition.
Reboot and your done.