ReactOS is a computer operating system intended to be binary-compatible with application software and device drivers made for Microsoft Windows NT versions 5.x and up (Windows 2000 and its successors). It is composed entirely of free software, by means of a complete clean room reverse engineering process.
Although the project is in the alpha development stage [...]

Popularity: 15% [?]

Windows XP Service Pack 3 Overview
Windows® XP Service Pack 3 (SP3) includes all previously released updates for the operating system. This update also includes a small number of new functionalities, which do not significantly change customers’ experience with the operating system. This white paper summarizes what is new in Windows XP SP3.  More
Popularity: 6% [?]
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Popularity: 6% [?]

QNX (pronounced either Q-N-X or Q-nix) is a commercial POSIX-compliant Unix-like real-time operating system, aimed primarily at the embedded systems market. As of September 12 2007, the source of the QNX kernel has been released for non-commercial use.

Description
As a microkernel-based OS, QNX is based on the idea of running most of the OS in the [...]

Popularity: 7% [?]

Magnussoft ZETA, previously yellowTAB ZETA, was an operating system formerly developed by yellowTAB of Germany based on the BeOS operating system developed by Be Inc.; because of yellowTAB’s insolvency, ZETA was later being developed by an independent team of which little was known, and distributed by magnussoft. As of February 28, 2007 the current version [...]

Popularity: 5% [?]