Getting down to one
A Microsoft account (formerly Windows Live ID) is the email address and password you use to sign in to all sorts of Microsoft devices and services, including Windows 8, Surface, Windows Phone, Xbox, Messenger, OneDrive, Hotmail, and more.
When you use the same Microsoft account to sign in everywhere, your contacts, calendar, music, photos, and files all travel with you, and you can use any of your services (Xbox, Xbox Music, OneDrive, OneNote, and so on) from any of your Microsoft devices.
We can help you figure out which of your accounts to use, depending on what's easiest to change, or what you're most attached to. We may even be able to help you switch the email address you use with certain services.