I Tried all the above method , but none of them worked for me . I didnt have any backup CD or a new OS to reinstall .
I was unable to get into Safe Mode nor was able to see task manager . All the keys F2,F8,F12 , ctrl+shift+esc , ctrl+alt+del
failed to do anything . I loose hoped and was going to see service centre , but still I thought to do a last try .
While still my laptop was showing a black screen with an arrow on it . I suddenly removed it battery .
I pluged in my charger and without battery I started . To my surprise it started again and all came back to normal
I thanks all the people to bringing up this forum and sharing all their experience which is reallyy helpful