Actually ive made the same post at blogspot but want to shift to wordpress so posting here…Many ppl out there are wondering if we can get back our linux installation after installling windows.this post is completely dedicated to it.To start of with windows uses the ntldr for activating the initial boot and linux uses grub….grub is more powerful than ntldr as we can
include a total of 26 o.s as far as i knw…..
our assumptions are that we had installed our grub on MBR,and u have a live cd wid u.
now when u install Xp after installing Linux ur grub gets overwritten with the ntldr and we have to get back our grub to dual boot.

Step 1:boot the live-cd and open the terminal

Step 2:fire up with the command sudo grub

step 3:If you are not sure which partition actually holds these files, use the command “find /boot/grub/stage1“
it will return something lyk (hd0,5)as in my case….

Step 4: Now, set the GRUB’s root device to the boot directory, like this:                       issue command “root (hd0,5)”
Note:remember there is a space btw root and (hd0,5)

Step 5:Once you’ve set the root device correctly,its time to setup grub now with the command “setup (hd0)”

if everything is done as said above then ur done with…….just reboot ur computer and edit ur grub conf file for any changes req…..