A friend recently tipped me off to Microsoft Support Knowledge Base Article ID 276304, “Error Message: Your Password Must Be at Least 18770 Characters and Cannot Repeat Any of Your Previous 30689 Passwords”.  As the title suggests, the error message this addresses is:

Your password must be at least 18770 characters and cannot repeat any of your previous 30689 passwords. Please type a different password. Type a password that meets these requirements in both text boxes.

Personally, I try to keep my passwords well under 10,000 characters.  With thee requirements, brute force hacking would have to be pretty efficient to compromise security.  Fortunately, seeing this problem in the real world is rather unlikely, and it only applies to Windows Server 2000.  So, you can rest easy if you choose to use slightly shorter Windows passwords.