By default, Windows NT 4.0 displays the name of the last person who logged on to the system. This informational exposure can pose a security threat, especially if a user's password can be guessed from the account name or the login environment. To turn off this "feature" :

Hive: HKEY_LOCAL_MACHINE
Key: Software\Microsoft\WindowsNT\CurrentVersion\Winlogon
Name: DontDisplayLastUserName
Type: REG_SZ
Value: 1 hide
Value: 0 don't hide

This can also be set via GUI tool, RegKey.exe from the Resource Kit. Use an indirect registry editor whenever possible.

If this hack has not been set, the registry location for the name of the last logon account is DefaultUserName .

Must have for NT advanced users