Fixing a zapped Ubuntu Master Boot Record!

NB only works with Grub version 1 (Ubuntu 6 etc). If you have Ubuntu 9 or 10 then you may have Grub2 which has a different fix.

This error can happen if you install Windows after Linux, or if you move partitions around with GParted. Sometimes the GRUB boot up panel is not there, sometimes you get ERROR 15 which means it can't find the root partition.

First boot up with Ubuntu CD as a Live session.
In Ubuntu Terminal (If you have grub2 this will not work)
sudo grub
> find /boot/grub/stage1
this gave me two locations, (hd0,1) and (hd0,4). The 0,1 was the one I wanted reinstated. so next command is
> root (hd0,1)
> setup (hd0)
> quit