Pop Banner when Windows Starts

If you want to display any kind of message to the user before he enters windows desktop, here's what you have to do:

Goto start->run and type regedit

This will open the registry editior.
Goto HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
\Windows\CurrentVersion\WinLogon

Create a new string value in the right pane called LegalNoticeCaption and enter the value you want to see. Create another string and name it LegalNoticeText. Edit the value to display what you want. (NOTE: In most cases these string values will already be there so you only have to edit the values)
Restart your computer.