Grub is short for GNU GRand Unified Bootloader. It’s a boot loader package from the GNU Linux project and allows you to choose which operating system or specific kernel to boot into.
I have linux (Fedora 14) as only OS in my laptop. However, in order to install Samsung Galaxy update via its tool (Kies). I use gparted free some disk and installed Windows XP (SP3). After this, the boot loader for linux was lost. Here are steps for restoration
1. boot up using ubuntu liveCD
2. open a terminal, sudo apt-update grub #install grub as it’s not installed on the livecd
3. sudo grub
4. find /boot/grub/stage1
hd0,0 # linux installed at sda1
5. root (hd0,0)
6. setup(hd0)
to add boot item for windows (my windows installed at sda2
title Windows XP
root (hd0,1)
makeactive
chainloader +1