Create Your Own Logon Message

Click Start, click Run, type regedit, and then click OK.
In the Registry Editor, drill down to the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
Right-click LegalNoticeCaption, click Modify, type My Windows XP Machine, and then click OK.
Right-click LegalNoticeText, click Modify, and then type your message.
Close the editor and your new message will appear at every log on.
This tip applies to computers that are part of a domain. For stand-alone or peer-to-peer networks, the custom screen appears just before the Welcome screen.