Microsoft will begin tightening the squeeze on Windows 2000 Server users from April of next year, at which point the product will cease to be available via retail or volume licensing. This is a fairly standard first step for the phase-out of Microsoft operating systems, and is more of an inconvenience for holdouts than starvation as such.
From November 2004, however, OEMs will no longer be able to supply Win2k Server either, meaning that companies still running it as standard and wishing to deploy new machines will have to buy 2003 licences and 'downgrade' to Win2k. It will still be possible to get downgrade CDs from Microsoft up until April 2006, but system builders will no longer be able to supply Win2k servers from November 2005. Support, which The Register helpfully pointed out a couple of weeks back seemed not to have noticed the launch of Windows 2003 Server, has now got its act together, with details available here.
As we say, the procedure is pretty routine, but the dates could present a problem for Win2k shops, because they mean that the rollout dates for Longhorn become a serious issue for them. As yet, rollout dates for Longhorn client are barely pencilled in, for somewhere from late 2005 to mid 2006. If something like this window is achieved, then we'll still have a lag before the server version shows, and even an optimistic view of Longhorn ship dates leaves a strong probability of the server release date overshooting April 2006. So sitting on your hands, skipping 2003 and waiting for Longhorn could start to require strong nerves. ®