Windows NT 4 Service pack

From Microsoft:

Service Pack 6a (SP6a) resolves the SP6 issue with Lotus Notes and other Winsock based applications and provides the latest updates to Microsoft Windows NT Workstation 4.0 and Windows NT Server 4.0 (including Enterprise Edition). SP6a contains known Year 2000 updates for Windows NT 4.0. These Year 2000 updates are also available as separate Web downloads that customers may apply to a Service Pack 4 system. Providing these options gives organizations the flexibility to choose which path is easier for them to address Year 2000 issues. SP6a is not a required upgrade for Year 2000; Microsoft recommends that each customer consult the SP6a documentation and then determine whether to deploy it.