All of my email contacts disappeared

I went to send an email and all of my contacts are gone! I haven't done anything different or used a different email address. I have had this address for years and the same computer for close to 5 years. I have never had to log on to windows live, I have an icon on my screen that I click on and it automatically opens. I am NOT a computer savvy person so if anyone can help, please "dumb it down" so I can follow  (:  I am lost without the addresses I have had stored for years...most I don't have written down, I got used to typing in the person's name and having the address pop up. Thanks for help and patience!!!!