Windows Server: How to add or remove a pre-logon welcome message

So you want to add a warning message to be displayed before a user logs on to the computer? No? Better, you want to remove it. Good, its all done in a few easy steps.

Locate the following registry key:

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

Add or empty the following values:

Name	Data Type	Value
LegalNoticeCaption	REG_SZ	This is the title of the window
LegalNoticeText	REG_SZ	This is a message displayed in the window

Source: http://support.microsoft.com/kb/315232