Open Notepad, copy the text below dashes.
Save the text to a file with a *.reg format.
Double click to import to your registry.

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Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"LegalNoticeCaption"="TYPE YOUR OWN STARTUP DIALOG BOX TITLE HERE"
"LegalNoticeText"="TYPE YOUR OWN DIALOG BOX CONTENT HERE"