When your password expired on your virtual box and you get locked out of the network, then you need to go through this process to resolve the issue, Phew! thankfully it only come to haunt you when every 3 months. :)
or essentially if it says you already have your machine added to the domain, what you need to do are
1. change your computer to a random workgroup.
2. without restarting, change it to your VALID domain. You will be prompted to key in name and password.