Recovering Linux installation after windows install

Since window does not detect GRUB, if you wanna add a windows installation later or recover your existing installation, you end up invariably losing your linux installation.

To recover it, insert the installation disk, enter the text based recovery, when the console opens up type
chroot /mnt/sysimage
This is where your system is mounted on the recovery console.
Then,
grub-install hd
like, hd0,hd1 etc. And reboot.