The default Windows XP logon screen displays a selectable list of all the user accounts available on the system.
Normally, all the accounts present (except for the Administrator account) are shown. This "friendly" XP interface was designed with home users in mind, where multiple users might share the same system and not need to have accounts hidden.
XP does support a method for hiding or revealing user accounts in the logon screen. Normally this method is used for concealing the built-in Administrator account (as well as other built-in system accounts such as the ASPNET account), which are not normally used. (To log in under the Administrator account in the first place, the system needs to be booted into Safe Mode anyway.)
A key in the Registry is used to describe which user names are hidden or revealed in the logon screen. Under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserList is a series of DWORD keys. The name of each key is the name of an account to hide, and setting the value of the key to 0 hides it from view. To add a new name to the list, simply create a new DWORD value with the name of the user account to hide, and set the key to 0. The account can be unhidden by either deleting the key or setting its value to 1. (Don't unhide the special system accounts such as ASPNET.)
Another way to conceal logon names is to switch Windows XP's logon style to the vintage Windows 2000 look-and-feel, where the user must type in a username and password manually. This provides the best possible security for concealing user names. To do this, go to User Accounts in the Control Panel, select "Change the way users log on and off", and uncheck "Use the Welcome Screen". Also, the administrator can set a system option to prevent the last logged-in user's name from appearing in the logon dialog. Edit HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon, add or change the DWORD value DontDisplayLastUserName, and set it to 1.
Serdar Yegulalp is the editor of the Windows 2000 Power Users Newsletter. Check out his Windows 2000 blog for his latest advice and musings on the world of Windows network administrators – please share your thoughts as well!