JSI Tip 0025 - Don't display Last user in logon dialogue.

HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionWinlogon

DontDisplayLastUserName REG_SZ
Range: 0 or 1

Default: 0 (false)

By default, Windows NT displays the name of the last person to log on in the Username space of the Logon Information dialog box. If you add this value entry and set it to 1, the Username space is always blank when the Logon Information dialog box appears.