how to reload grub of linux after reinstalling xp

generally the user has to install windows and then they should install linux.when they install linux the windows bootloader will be overwritten by linux bootloader grub. when suddenly ur xp is affected or corrupted u will reinstall xp at that time linux os will be there (eg.ubuntu)but only that bootloader grub will disappear so u are not able to boot in linux if u want to boot in linux u have to just reload the grub using the livecd with the help of the following commands
You need to know this means that it can’t find the grub.conf file.

1. Boot your computer up with Ubuntu CD

2. Open a terminal window or switch to a tty.

3. Go SuperUser (that is, type “sudo -s”). Enter root passwords as necessary.

4. Type “grub”

5. Type “find /boot/grub/stage1″. You’ll get a response like “(hd0,1)”.

Use whatever your computer spits out for the following lines.

6. Type “root (hd0,1)”, or whatever your hard disk + boot partition numbers are for Ubuntu.

7. Type “setup (hd0)”, to install GRUB to MBR, or “setup (hd0,1)” or whatever your hard disk + partition nr is, to install GRUB to a partition.

8. Quit grub by typing “quit”.

9. Reboot and remove the bootable CD.

Note:- In the above procedure hd0,1 is an example it might be different in your case