If any one use dual boot system then after installing windows again we lost GRUB loader. It can recover in various method. Here i discuss GRUB recovery using Live cd. For this we have to boot our system by Live cd.Then in terminal
sudo fdisk -l
to see the partitions,we'll see something like this..
Disk /dev/hda: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/hda1 * 1 1275 10241406 c W95 FAT32 (LBA)
/dev/hda2 1276 2187 7325640 83 Linux
/dev/hda4 2806 9963 57496635 f W95 Ext'd (LBA)
/dev/hda5 2806 4080 10241406 b W95 FAT32
/dev/hda6 4081 5355 10241406 b W95 FAT32
/dev/hda7 5356 6630 10241406 b W95 FAT32
/dev/hda8 6631 9963 26772291 b W95 FAT32
Here my linux partition is hda2.
Now we have to type
cd /boot/grub
then type
grub
we'll see
grub>
in terminal.
then type
grub> root (hd0,1)
grub> setup (hd0,0)
grub>quit
Now reboot your Computer and watch.
Spacial thanks to Suzan bhai & Asad
Note: For hda1,sda1 it'll be (hd0,0),hda2,sda2 it'll be (hd0,1),hdb1,sdb1 it'll be (hd1,0)