i haven't tried this but found it in a search.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\UserLis t.
Note: There is a space between Windows and NT.
Add the username you wish to hide as a DWORD value. Set the value to 0 (zero). This will prevent the user from showing up on the welcome screen. You will need to press CTRL-ALT-DEL twice at the logon screen to get the old Win2K logon, to be able to logon to the account you've hidden. Adding a username and setting the value to 1 will cause that user, such as Administrator, to show up on the Welcome screen as well.
1 fast and 1 slow