To pop a banner which can contain any message you want to
display just before a user is going to log on, go to the key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVers
ion\WinLogon

Now create a new string Value in the right pane named
LegalNoticeCaption and enter the value that you want to see in the
Menu Bar. Now create yet another new string value and name it:
LegalNoticeText. Modify it and insert the message you want to
display each time Windows boots. This can be effectively used to
display the company's private policy each time the user logs on to
his NT box.


It's .reg file would be: 
 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVer
sion\Winlogon]

"LegalNoticeCaption"="Caption here."