It marked the company's entry into the corporate computing environment, designed to support large networks and to be portable, compiled for Intel x86, DEC Alpha and MIPS based workstations and servers.

[3] Windows NT began as a rewrite of the OS/2 operating system, which Microsoft had co-developed with IBM but failed to gain much traction against Unix, with vendor Sun Microsystems dominating the market for powerful desktop workstations.

When Windows NT premiered, their sales were limited by high system requirements, and a general lack of 32-bit applications to take advantage of the OS's data processing capabilities.

On December 31, 2000, Microsoft declared Windows NT 3.1 obsolete and stopped providing support and updates for the system.

The origins of Windows NT date back to 1988,[5] where Microsoft had a major foothold on the personal computer market due to the use of its MS-DOS as the operating system of IBM PC compatibles.

Nathan Myhrvold, who had joined Microsoft after its acquisition of Dynamical Systems Research, identified two major threats to Microsoft's monopoly—RISC architectures, which proved to be more powerful than the equivalent Intel processors that MS-DOS ran on, and Unix, a family of cross-platform multitasking operating systems with support for multiprocessing and networking.

[6]: 34  While the widespread use of Unix was hindered by the need to adapt programs for each individual variant, Bill Gates believed that the combination of a Unix-like operating system with RISC processors could be a market threat, prompting the need for Microsoft to develop a "Unix killer" that could run on multiple architectures.

[5] Gates had also hired Dave Cutler from Digital Equipment Corporation to assist in developing the new operating system; Cutler left DEC after the cancellation of the PRISM architecture and its MICA operating system, and agreed to join Microsoft on the condition that he be able to bring a number of staff members from his team at DEC with him.

[10] Both Microsoft and IBM wanted to market an operating system that appealed to corporate "enterprise software" customers.

However, since Microsoft also wanted to capture market share from Unix on other computing platforms, they needed a system design that was more portable than that of OS/2.

The company was eager to silence naysayers who speculated that NT wouldn't be on the market until 1994, and had planned to present the new OS at COMDEX in 1990.

[6]: 165 [15] The demonstration was positively received; PC Magazine called Windows NT "the modern reinvention of the operating system", but at the same time claimed that it was unlikely that the promised backward compatibility would be kept for the final release.

[19][20] Concerns were also raised over NT's memory usage; while most computers of the era shipped with 4 megabytes of RAM, 16 MB was recommended for NTs.

The version for workstations, but not Windows NT 3.1 Server, was additionally available in Danish, Finnish, Italian, Norwegian and Portuguese.

[31] During the planning phase it was clear that this would cause Windows NT to have higher memory consumption than all previous operating systems.

[6]: 54  To meet this goal, the architecture of Windows NT was designed so that the operating system core was isolated and applications could not access it directly.

[6]: 54  The Mach kernel followed a similar concept by moving the APIs to components which operated in user mode as applications, these could be changed and new ones could be added.

[8]: 6 Despite all these goals, the performance of the operating system was optimized where possible, by adapting critical sections of the code to fast execution speed.

[6]: 151 Therefore, Windows NT was positioned as a high-end operating system in an interview with the product manager David Thacher.

It was not designed to replace Windows 3.1 completely, but it should rather supplement Microsoft's product palette with an operating system for critical applications.

[35] The Virtual DOS Machine (VDM) is sometimes also viewed as a subsystem, but is, strictly speaking, a normal 32-bit Windows application.

[35] Windows NT 3.1 provides a boot manager called NTLDR which is loaded during the startup process of the operating system on x86-based computers.

[35] Similar to Windows for Workgroups, files and printers can be shared and the access rights and configuration of these resources can be edited over the network.

[35] Windows NT 3.1 supports the then-new Unicode standard, a character set which allows multiple languages to be displayed.

Windows NT 3.1 supports multiple platforms: Aside from the x86 architecture, it runs on computers with DEC Alpha or MIPS (R4000 and R4400) processors.

[54] The Advanced Server, intended to be the successor to the unsuccessful LAN Manager product, was technically much superior to its predecessor, and only failed to gain success because it shared the same problems with its workstation pendant, such as the low performance running 16-bit applications.

[55] The Advanced Server provided a financial advantage for large networks because its price was not dependent on the number of clients, unlike its competitor Novell NetWare.

[49] With Windows NT, Microsoft entered a market it could not previously address and which was mostly dominated by Unix, Novell NetWare and OS/2.

[56] A test performed by the InfoWorld magazine in November 1993, where the networking capabilities of several operating systems were tested, showed that Windows NT 3.1 was seriously lacking in inter-client communication: it could only connect to its own server via NetBEUI; attempts to connect to Unix, NetWare and OS/2 all failed because no client software was available.

[59] It was recognized that Windows NT would dominate the desktop market as soon as the hardware became powerful enough to run the operating system at an acceptable speed.