If you want to use windows 8 with Linux here is the solution.
If the Grub loader is not loading after windows 8 install, first you need to boot with a Live CD.
Then run these commands as root:
To find the drive where Linux is installed run the following command:
Device Boot Start End Blocks Id System
/dev/sda1 * 1 9330 74936320 83 Linux
In my case sda1 is the drive where Linux is installed.
Then you need to run the following commands:
mount /dev/sda1 /mnt/
mount -o bind /dev /mnt/dev
mount -o bind /proc /mnt/proc
cp /proc/mounts /mnt/etc/mtab/
chroot /mnt /bin/bash
And the final step is to remove the Live CD and restart your PC.