When a user gets logon You might want to have a message pop up to display a Welcome message. This can be used to display Instructions,Company Policy,User related information,any alert,warning or anything you wish to do .

Navigate to:

HLM\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\WinLogon

Create a new String Value here called LegalNoticeCaption. Enter whatever messag you want to see in the Title bar of the message that you wish to pop up. Now create another new String Value called LegalNoticeText. Modify it to the message you want to display each time Windows boots.The message will be displayed at the next logon.

This trick works with Windows 7 as well.