. Suppose linux lies on /dev/sda6 (fdisk -l)
# mount /dev/sda6 /mnt # mount the linux partition on /mnt
# mount –bind /proc /mnt/proc # mount the proc subsystem into /mnt
# mount –bind /dev /mnt/dev # mount the devices into /mnt
# chroot /mnt # change root to the linux partition
# grub-install /dev/sda # reinstall grub with your old settings

Boot liveCD.  Find the Linux partition under /dev and then find the bootable partition under fdisk.  Lets say its /dev/sda1

# mount /dev/sda1 /mnt

# mount–bind /proc /mnt/proc

# mount –bind /dev/ /mnt/dev

# chroot /mnt

# grub-install /dev/sda

Try this before you start crying.