Recently Windows Live introduced Single-Use code a very simple and effective way to Sign-In to your Live account from a public computer like at the library or school. You can now use a Single-Use Code instead of your password for added security.
Requesting a Single-Use Code:
Each Single-Use Code can be used only one time, but you can request one whenever you need one. When you request a Single-Use Code, you receive it in a text message to a mobile phone number that you’ve added to your Windows Live account.