How to recover grub 2

You need a live CD of Ubuntu 10.10 (in my case )
Once you boot to the LIVE CD, open a terminal an and type these commands:

1.Firstly, you need to find out on which partition your Linux system is installed:

   sudo fdisk -l

(in my case, it's "sda1")

2.Now, we must mount this partition:

  sudo mount /dev/sda1 /mnt

3.Install grub to the partition you've mounted:

  sudo grub-install --root-directory =/mnt/ /dev/sda
4.Restart your computer. As previous Grub2 entries are removed, run the following command to restore them:
  sudo update-grub