Change the Message Shown on the Logon Box

Start/Run/Regedit

"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\ CurrentVersion\Winlogon"

Value Name: LogonPrompt, Data Type: REG_SZ (String Value). Create a new string value named 'LogonPrompt' and enter the text you want to display. The default message is: 'Enter a user name and password that is valid for this system.' This feature can be used in conjunction with the Legal Notice Dialog Box Before Logon tweak.

Reboot your computer.