The storage array is not accessible using the Dell Powervault ME4 Web UI after losing the username/password to login.
U144, U840, and ME4 storage arrays
The account name and password have not been maintained.
You will need to access the storage array directly. Connect a microUSB cable from your computer to the port labeled CLI on the controller, in the rear. Connect via serial using PuTTY (or other terminal utility).
Password: (serial number of the controller)
This deletes the user and password you set. If you have lost the username and/or password, this is the one you want to run first (or second, if you ran restoredefaults)
This proven method requires a couple of extra steps to create a new password.
Password: (blank, no password)
This enables the first run web wizard, which allows you to re-establish a new username and a new password. The username "admin" is not allowed.