Windows NT 3.51

Windows NT 3.51 is the third release of Microsoft's Windows NT line of operating systems. It was released on 30 May 1995, nine months after Windows NT 3.5. The release provided two notable feature improvements; firstly NT 3.51 was the first of a short-lived outing of Microsoft Windows on the PowerPC architecture. The second most significant enhancement offered through the release was that it provides client/server support for interoperating with Windows 95, which was released three months after NT 3.51. Windows NT 4.0 became its successor a year later; Microsoft continued to support 3.51 until 31 December 2001.
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Overview
The release of Windows NT 3.51 was dubbed "the PowerPC release" at Microsoft. The original intention was to release a PowerPC edition of NT 3.5, but according to Microsoft's David Thompson, "we basically sat around for 9 months fixing bugs while we waited for IBM to finish the Power PC hardware". Editions of NT 3.51 were also released for the x86, MIPS, and Alpha architectures.

Despite the significant difference in the kernel base, Windows NT 3.51 is readily able to run a large number of Win32 applications designed for Windows 95. Most recent 32-bit applications will not work as the developers have prevented their application from working with any Windows version earlier than Windows 98, also because some applications do not work properly with the older Windows NT 3.51 interface. Despite this, Microsoft in their application releases muddied the issue, releasing 32-bit versions of Microsoft Office right up to Office 97 SR2b, but relying upon 16-bit versions of Internet Explorer technology. This is probably because 32-bit versions of Internet Explorer 4.0 and later integrated with the Windows 95 desktop, and NT 3.51 still used the Windows 3.1 desktop. Later on, up to IE 5.0, but not later 5.x versions, were offered.

Microsoft also released test versions of a shell refresh, named the Shell Technology Preview, and often referred to informally as "NewShell". The update was designed to replace the Windows 3.x Program Manager/File Manager based shell with a Windows Explorer-based graphical user interface. The release provided capabilities quite similar to that of the Windows "Chicago" (codename for Windows 95) shell during its late beta phases, however was intended to be nothing more than a test release. There were two public releases of the Shell Technology Preview, made available to MSDN and CompuServe users: 26 May 1995 and 8 August 1995. Both held Windows Explorer builds of 3.51.1053.1. The Shell Technology Preview program never saw a final release under NT 3.51. The entire program was moved across to the Cairo development group who finally integrated the new shell design into the NT code with the release of NT 4.0 in July 1996.

Five Service Packs were released for NT 3.51, which introduced both bug fixes and new features. Service Pack 5, for example, fixed issues related to the Year 2000 problem.

NT 3.51 was the last of the series to run on a Intel 80386 processor. This, its ability to use HPFS partitions (which Windows 2000 and later could not), and its ability to run at least some of the common control API, means that it still finds a place for occasional use on older machines.