I was recently using a captured image for mass deployment where I was using the CopyProfile key to managed default user profile settings. After using this setting in your Unattend.xml file, during the first user log in, it will show Administrator as the user. Not really a big deal to IT people, but this can be confusing to an average user that needs to log in with their domain account. To fix this, I added the following Run Command Line step to my task sequence:
reg add HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionPoliciesSystem /v DontDisplayLastName /t REG_DWORD /d 1 /f
And if you prefer to enforce this with group policy (several organizations do), it’s located under Security Settings -> Local Policies -> Security Options -> Interactive Logon.
Both of these options clear the last user logon name history and will provide the user with a blank username field.