sometime you install windows (or any other operating system) and loose your linux grub
i tell you how to do this with GRUB2
1)Boot from LiveCD Desktop (ubuntu 9.10 or 10.4 or later 32 or 64 bit)
2)Open a terminal by selecting Applications, Accessories, Terminal from the menu bar.
3)Determine the partition with the Ubuntu installation.
sudo fdisk -l
output is omething like this : Device Boot Start End Blocks Id System
/dev/sda1 * 1 3225 25904781 7 HPFS/NTFS
/dev/sda2 3226 9730 52244789 f W95 Ext'd (LBA)
/dev/sda5 3226 6325 24900718+ 7 HPFS/NTFS
/dev/sda6 6326 6568 1951866 82 Linux swap / Solaris
/dev/sda7 6569 8028 11720704 83 Linux
/dev/sda8 8028 9730 13670400 83 Linux
my linux is on sda7 partition 4)Mount the partition containing the Ubuntu installation.
sudo mount /dev/sda7 /mnt 5)The below command will reinstall the GRUB 2 files on the mounted partition to the proper location and to the MBR of the designated device.sudo grub-install --root-directory=/mnt/ /dev/sda
6)Reboot and enjoy
