i tried restoring MBR using windows vista recovery disk...
after that i was able to mount windows xp partition (which was unable to mount only that windows xp partition before inserting vista recovery disk)
Then i inserted ubuntu live cd
and i followed the CHROOT method i didnot do reinstall grub in step 9&10 (which was suggested by one of my friend)
after that i was able to run triple boot
Than'Q' Eddy & Andrew Thomas for playing a role in solving my Issue...