actually i have figured out the problem myself...
this is happening because we are living outside united states...
I'm living on India, and churana is available only in united states, so bing doesn't provide personalisation.
here's the solution...
go to bing homepage and sign in..
go to settings and change country to united states
then open personalization page and delete Cortana data...
that's it Cortana would be new as ever ...!!!