MS-DOS in Windows 9x

Windows 95, Windows 98, and Windows Me included versions of MS-DOS that included major changes to improve cooperation with the Windows environment. They are used to bootstrap Windows on boot, as well as to provide the environment for virtual DOS machines. These versions internally continued the original MS-DOS versioning, although they use the respective Windows version branding. They were never available as standalone products, although such unofficial repacks exist and tend to be mislabeled as actual standalone versions.

The integration of MS-DOS into Windows was a subject of a major lawsuit by Caldera, the developer of the competing DR-DOS operating system, who viewed this as an anticompetitive measure. The company has later demonstrated Windows 9x running on top of a custom version of DR-DOS that included the functionality necessary to boot the environment. In 2000, Microsoft settled out of court for an undisclosed sum, which was later revealed to be $280 million.

MS-DOS 7.00
MS-DOS 7.00 (codenamed Jaguar) is included as part of early Windows 95 versions. Compared to standalone MS-DOS,  was combined into   (initially called  ), and the original file is used as a configuration file to control Windows integration. Also introduced was support for long file names on the FAT file system and a splash screen. Although MS-DOS 7.00 was primarily designed for Windows 95, older versions of Windows can still run on top of it. However, this is the last version of MS-DOS capable of running Windows 3.1x, as an error prevents it from starting on MS-DOS 7.1 and later.

There were plans to release a standalone version of MS-DOS 7.00 as late as autumn 1993. The features considered for inclusion included multi-tasking, networking, and better support to MS-DOS 6.x for users who preferred the command-line interface and highly price conscious OEMs. It is unknown whether any builds were distributed to testers or developers but there are evidence suggesting builds were made. In Windows 95 build 189,  has the branding of MS-DOS 7.00, suggesting that it was still under development as a separate product in late 1994.

Several fake builds of this version have been circulating on the Internet. Most of those fakes were made by modifying files from early Chicago builds and adding files from other versions of MS-DOS.

MS-DOS 7.10
MS-DOS 7.10 is included with Windows 95 OSR 2.x and Windows 98. This version of MS-DOS includes FAT32 support.

China DOS Union repack
An unofficial repack of the MS-DOS subsystem in Windows 98 was made by the China DOS Union in 2003 and is often mislabeled as an actual official release of MS-DOS 7.10. The system includes various optional add-ons which install additional third-party programs and graphical shells on top of MS-DOS.

MS-DOS 8.00
MS-DOS 8.00 was included with Windows Me and is the final version of MS-DOS. When installed with Windows, it removes the ability to use real mode MS-DOS without Windows as it skips processing of  and. However, this limitation is not present when an MS-DOS startup disk is created from the user interface or the MS-DOS prompt. This version is also used for the MS-DOS startup disk option in Windows XP through to Windows 8.1.