If you disable the XP Welcome screen and require the Ctrl+Alt+Delete key combination as part of the logon process, users are presented with the standard Log On to Windows dialog box where they need to supply a username and password. By default, this box displays a message stating, “Enter a user name and password that is valid for this system”. While this message may suit you fine, it can also be changed with a very simple registry edit.
To personalize or customize this message, open Regedit and browse to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon. The value that you’ll want to create is a REG_SZ value called LogonPrompt. Change this value and enter your message of choice, for example, “By entering your username and password below, you confirm that SuperCorp has given you permission to use this system”. After a reboot, this message will appear in the logon dialog box.