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Article ID: 153762 - Last Review: February 21, 2007 - Revision: 2.2

This article was previously published under Q153762


This article describes how to set up Windows to dual boot with MS-DOS on a computer that was originally set up as a Windows-only computer. To dual boot, the computer partition must be a file allocation table (FAT) partition and not a Windows NT file system (NTFS) partition.


  1. Start the computer from an MS-DOS floppy disk that contains the file. Sys the boot drive to MS-DOS by typing the following command at a command prompt:
    a:\>sys c:
    After you type this command, you receive a system transferred message when the procedure is finished.

    NOTE: This command disables the Windows boot loader so that the computer boots MS-DOS when booting from the computer's hard disk. You must repair the Windows boot loader after you use the following steps.
  2. Reboot the computer from the computer's hard disk to a command prompt and install MS-DOS on the computer if it is not already installed.
  3. After you completely install MS-DOS and reboot, restart your computer by using the Windows Setup disks. During Setup, select R to repair Windows.

    NOTE: You need to repair only the Windows boot sector. Do not choose to inspect the registry files, the Windows system files, or the Windows boot environment during this procedure.
  4. After you repair the Windows boot sector, you need to manually edit the Boot.ini file to include an option to boot to MS-DOS. The Boot.ini file is a read-only, hidden, system file that is located in the root folder of the boot drive. Add the following line to the Boot.ini file under the operating systems section:
    c:\="Microsoft DOS".
The next time that you reboot the computer, you have an option to choose MS-DOS on the Windows Start menu.

You can use the procedure in this article to enable dual booting between Windows NT and Windows 95. To dual boot Windows 95, boot the computer to MS-DOS and install Windows 95. A Windows 95 installation is Windows NT-aware and does not overwrite NT boot loader information when you use this procedure.

  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows 2000 Professional Edition
  • Microsoft Windows 2000 Datacenter Server
  • Microsoft Windows NT Workstation 3.5
  • Microsoft Windows NT Workstation 3.51
  • Microsoft Windows NT Workstation 4.0 Developer Edition
  • Microsoft Windows NT Server 3.5
  • Microsoft Windows NT Server 3.51
  • Microsoft Windows NT Server 4.0 Standard Edition
kbinfo kbsetup KB153762
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