A registry tweak to have a message pop up just before login, prompting a user to hit the OK button, is another way.
Create a test file, called something like legalmessage.reg, and place the following items in it:
REGEDIT4
[HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Winlogon]
"LegalNoticeCaption"="Welcome to Southern Office Products"
"LegalNoticeText"="Access for Authorized Users Only!"
Of course you can substitute your messages accordingly. Then just double-click on the file you created, answer OK to the message about adjusting the Registry settings, and if everything is typed correctly, the next time your boot up, you should get the message!
Good luck,
dwallace