W2K service pack 4 is now available for download from M/S. Just click on Windows Update on your "start" menu, and you will find it as a "critical update".
You download a 500K+ module which examines your system and then down loads and installs the updates which apply to your configuration. In my case, there was over 14MB of updates. Be prepared to spend some time.
Take a backup before you start.
I installed service pack 4 yesterday morning and have seen no problems with it.
An up to date Windows sytem is a happy system.