Windows Services for UNIX (SFU) is a discontinued software package produced by Microsoft which provided a Unix environment on Windows NT and some of its immediate successor operating-systems. SFU 1.0 and 2.0 used the MKS Toolkit; starting with SFU 3.0, SFU included the Interix subsystem, which was acquired by Microsoft in 1999 from US-based Softway Systems as part of an asset acquisition. SFU 3.5 was the last release and was available as a free download from Microsoft. Windows Server 2003 R2 included most of the former SFU components (on Disk 2), naming the Interix subsystem component Subsystem for UNIX-based Applications (SUA). In Windows Server 2008 and high-end versions of both Windows Vista and Windows 7 (Enterprise and Ultimate), a minimal Interix SUA was included, but most of the oth