NT Security Option

Not sure if this is what you are talkin about, your post was a little unclear. But try this.

1. Start Registry Editor (Regedt32.exe).
2. Locate the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon
3. Locate and delete the LegalNoticeText value.
4. There is another LegalNotice Entry. I think it is for the title bar, delete that too.

If these entries are not here, the the box that is coming up is from a system policy, unless you have Admin rights, you probably can't remove it. Try running the system policy editor.