Windows 2000 has a limit of 512 Characters when using the Group Policy
Editor
to create the LegalTextNotice / Logon Message.
Windows XP supports 1024 through the Group Policy Editor. XP was changed
to use a Multivalue String and supports carriage returns - unfortunately, it
is not
backward compatible, so you will run into display issues if you try to use a
setting
created with XP on a W2K machine.
We are working towards unifying the OSes with regard to this value,
hopefully in
an upcoming W2K service pack.
As a work around, the registry key itself supports a much larger amount of
characters.
You could deploy a larger Logon Message by deploying a registry change
through a computer
startup script, or, I have seen customers successfully import a modified
INF, with a larger
amount of text, into the security policy. Just test in your lab, and don't
edit it after the fact through the GUI.