for security, the Domain server may have been configured to enforce the regular changing of User-Password, so every few weeks, you are getting the message:
and you need to define a new password:
On your next Logon to the network, you are then using the new password, but you will also be prompted now for a Windows Login Password:
By changing the network password, Windows could not login to the local Windows system with the network password, since the local Windows Logon-password had not yet been changed !
For most users, it is just annoying to have now to change also the Windows Logon-Password, but there is a very simple method to avoid this:
Goto the Control-Panel: "Passwords" and select "Change Windows Password..":
Important: since we want to change only the Windows Password, make sure that there is NO Check-mark on the "Microsoft Networking":
In the "Change Windows Password" dialog, enter your current Windows Login password, but enter NOTHING (leave it BLANK) in the fields for the new Passwords, then select 'OK':
Windows will not bother you anymore with the "Windows Logon", even if you have to change again your Network password.