Windows Live mail 2011 Calendar events all gone - help

I'm on Windows 7

I've used Live mail 2011 calendar for over a year without ever signing in the calendar has all my important events/birthdays etc.

Since creating an account and signing in these have now all vanished and I have a blank calendar.

How can I restore my calendar to its previous state?

(I have run regular monthly backups to an external drive - will the original be stored on it ? if so where and how do I restore it)

thanks

Desperate Bob