Have you ever wondered about how Windows Live suite of software and services recognize you in various Web pages and brings you all the customized personal settings you left when you last visit?!
The whole process is with aid of something called Windows Live Unique ID! The unique identifier (ID) is a 64-bit number that Windows Live assigns to you at registration. Windows Live stores your unique ID in a cookie on your computer and the rest is as simple as you may never noticed before!
When you sign in to a site or service that requires a Windows Live ID (The e-mail address and password that you use to sign in to Windows Live programs and services such as Windows Live Hotmail and Windows Live Messenger; Microsoft services such as Xbox LIVE, MSN, and Office Live; and anywhere else that you see the Windows Live ID logo.) , Windows Live encrypts and sends this unique ID to the site to determine whether you are the same person from visit to visit. Sites can use your unique ID to maintain your settings and preferences every time you return.
It’s also interesting to know that if you close your account, Windows Live does not reuse your unique ID. If you open a new account, you'll get a new unique ID!
