Windows NT 2.1

Windows NT 2.1 is a basic 16-bit operating system that was an upgrade from Windows 2.1, no new programs came with NT 2.1 but there was an available version of this called: NT 2.1e This is the extension for Windows NT 2.1 and allowed you to access 32-bit programs in 16-bit.

Versions of NT 2.1
The versions allowed for Windows NT 2.1 were:

NT 2.1 Server

NT 2.1 Workstation

NT 2.1 Workgroups

NT 2.1 Advanced Server

Extra Information
Windows NT 2.1 is an improved version of Windows NT 1.01 and looks similar to Windows 2.03, due to it not being massively different. Support ended on December 31st of 1999, while extended support lasted until 2001.