Why Windows 8 says that your Password is Incorrect?

Are you trying to log into Windows 8 using your Windows Live ID (or Microsoft Account) but the system thinks that your password is incorrect? Here’s a possible reason. 

Windows 8 and Microsoft Account (or Windows Live ID)

Microsoft has made one important change in Windows 8 around user accounts. You can sign into Windows 8 using your online Microsoft Account (the new name for Windows Live ID) instead of creating a local user account. There are two advantages here:

1. If you work across multiple computers that are connected to the same Microsoft Account, your various Windows settings, themes, passwords and app purchases will automatically sync* across all these computers.
2. This is good from security point of view as well. When someone logs into a new Windows 8 computer using your Microsoft Account, the system will send you an instant email notification to confirm the same. You can easily disable that connection by following a a link available in the same email message.

[*] If you have used the Google Chrome browser that is connected to your Google Account, you know how the browser can sync your bookmarks, extensions and installed apps across multiple computers where you have logged in with the same Google Account. Microsoft is taking a similar approach but at the larger OS level.

Why Windows 8 thinks that your Password in Wrong?

I encountered a strange issue yesterday. I connected my Windows 8 machine to my Windows Live account but whenever I tried logging into the machine, the system would say that the password is wrong though I was entering the correct password (I could still sign-in to my Hotmail and SkyDrive account using the same Windows Live credentials).

It turned out that the problem was related to the length of the password that I was using with my Windows Live ID.
The password field on the Windows 8 login screen can only accept 15 characters so if you are using a long password, the system won’t let you in. It looks like a UI bug to me or they could have set 15-characters as the new maximum length of passwords in Windows 8.
In either case, if you have the habit of using “really” long passwords, you might have to visit your Windows Live profile and change your password to a shorter less-secure password to get inside Windows 8.