1.RxDOS

Fast MS-DOS clone that supports very large disk drives, FAT32 volumes, and Windows 95/98 Long Filenames.

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2.React OS

ReactOS is a free and open-source operating system based on the Windows NT architecture design, providing support for existing applications and drivers and an alternative to the current dominant consumer and server operating systems.

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3.OpenSolaris

OpenSolaris is an operating system (OS), an open source project licensed under CDDL, and a community. The project’s goals are innovation, collaboration, and the extension of OpenSolaris technology.  OpenSolaris is free, open source, and well-suited for desktops, laptops, servers, and data centers

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4.Slackware

Slackware Linux by Patrick Volkerding is an advanced Linux operating system, designed with the twin goals of ease of use and stability as top priorities. Including the latest popular software while retaining a sense of tradition, providing simplicity and ease of use alongside flexibility and power, Slackware brings the best of all worlds to the table.

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