Archived from groups: microsoft.public.windowsnt.misc (More info?
The page http://www.microsoft.com/windows/lifecycle/default.mspx
licenses for NT 4.0 Workstation ceased being available (to anybody) on 30 Jun 2003.
I expect you could purchase a later generation qualifying product, say Win2k and
use your 'downgrade' rights to run NT 4.0 instead if you wish. The legality of
this point is a bit tricky, perhaps some others would like to share their
experiences of how they are dealing with this licensing issue.