Customize Logon and Security Dialog Title

Start Run Regedit

Go to: HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NT CurrentVersionWinlogon

Modify/Create String Value of Data type REG_SZ Named Welcome
Value Data: 0 = Disabled / 1 = Enabled

Exit Registry / Reboot

17. Customize Logon Box Message

This is the message displayed on the Classic Logon box, not the XP ?Welcome? logon screen

Start Run Regedit

Go to: HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NT CurrentVersionWinlogon

Modify/Create String Value of Data type REG_SZ Named LogonPrompt
Value Data: Enter the text of the message

Exit Registry / Reboot
source:here