Upgradeability
An "Option Pack" was available as a free-bundled CD starting around 1998, which included IIS 4.0 with Active Server Pages, FrontPage Server Extensions, Certificate Server, MTS, MSMQ, CDONTS, Internet Authentication Service (IAS), Indexing Service, Microsoft Management Console 1.0, Microsoft Site Server, SMTP and NNTP services and other new software.
Several features such as Distributed File System and Windows NT Load Balancing Service (WLBS) were delivered as addons for Windows NT Server 4.0. The Routing and Remote Access Service was also a downloadable feature which replaced Windows NT 4.0's separate RAS and Multi-Protocol Routing services.
The last version of Microsoft Office to run on Windows NT 4.0 is Office XP.
Read more about this topic: Windows NT 4.0