Beginning on Friday, July 20th, Live ID began its transition to Microsoft Account. At a high level, this is primarily a name change from Windows Live ID to Microsoft account. The sign-in page for Windows Live ID will be updated and adopt the new name. However, this will not change how you sign in to your services, as you will use the same email and password.
This will be a transition that happens over time as content references across the Microsoft.com network (and on external sites) abound. There will be a link on the sign-in page which explains this name change and references that you may see both names for a while, but they are one in the same.
To reference the name change, please click here.