Dual-booting all versions of Windows and Linux
Install MS-DOS 7.10 on a Window NT that uses NTFS
Last reviewed: September 2008
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About adding MS-DOS 7.10 (FAT or FAT32) to a Windows NT that uses NTFS
You can install MS-DOS 7.10 on a computer with Windows NT using NTFS already installed so you can select either MS-DOS or Windows NT on startup (a dual-boot is created). There should be no loss of data and no commercial utilities are required.
However, you must create a new Primary partition (drive) at the end of the NTFS partition(s) for the MS-DOS installation. If you don't have free space (unallocated) at the end of the hard disk, you can resize (smaller) the existing partition with PartitionMagic (commercial), or with GParted (free, and just as good!) on the GParted Live CD (90 MB) or on Ubuntu Live CD (700 MB), or with a variety of other partitioning/resizing utilities. Unfortunately, the free Easeus Partition Manager Home Edition (8 MB) does not appear to work with Windows NT.
MS-DOS must be installed on a Primary FAT32/FAT partition on the first hard disk (seen as Disk0 at boot time).
You must not use this page if your current Windows uses the FAT file system. Use the instructions in Install MS-DOS on a Window NT that uses FAT - there are substantial differences in the procedures.
The MS-DOS version 7.10 that comes with Windows 98SE was used in testing. The single hard disk used was a 40 GB Western Digital all of which was used by Windows NT Workstation 4.0 (Build 1381, SP1 updated to SP6) on a single NTFS partition.
Initially Windows NT v4.0, SP1, was used successfully but proved unfriendly because of the disk size limitation (7.8 GB) and the NT installation partition size limitation. Thereafter, the SP1 was updated to SP6 before the procedure described here and this proved more satisfactory because the entire disk could be used from the very start.
How MS-DOS will work with NTFS
The Windows NT boot loader (NTLDR) will gladly boot to MS-DOS provided a few conditions are met.
Unallocated free space is created at the end of the NTFS partition. FAT will be used if less than 2048 MB is allocated to MS-DOS; if greater than that, FAT32 can be used.
Fdisk (preferably) is used to create a Primary partition in the Unallocated space and that partition is Formatted with FAT32 or FAT. When booted to MS-DOS, any NTFS partition is ignored and the FAT or FAT32 Primary partition is automatically the C: drive.
The SYS C: command in Btsect (btsect25.zip) creates a MS-DOS boot sector on this C: (it's the FAT/FAT32 drive) and also copies Command.com, Drvspace.bin, Io.sys, and Msdos.sys to C:. Btsect then copies the MS-DOS boot sector of C: to C:\Bootsect.dos.
The newly created Bootsect.dos must now be copied to the root of the NTFS partition that contains the NT boot files - the Active partition. This is not a problem if MS-DOS is on a FAT partition because Windows NT gives access to FAT partitions but not to FAT32. If Bootsect.dos is on a FAT32 partition, it must first be copied to a media accessible by Windows NT. This is usually a floppy disk or a hard disk FAT Logical partition - Bootsect.dos can be copied from there to the NTFS partition when booted to Windows NT.
Adding the line, c:\bootsect.dos=" dos ", to boot.ini completes the dual-boot creation.
The NTFS partition always remains the Active partition and Windows NT always retains its ability to boot throughout the process. MS-DOS will not be independently bootable at any stage (unless its partition is made Active!).
Preparation: Dual-Boot MS-DOS 7.10 on a Windows NT that uses NTFS
Procedure: Install MS-DOS 7.10 on a Windows NT that is using NTFS
Reboots are important. Please follow on-screen instructions.
Finished! You now have a boot menu containing both operating systems.
Boot to 'MS-DOS 7.10' and install your full MS-DOS 7.10. Installing or re-installing MS-DOS from DOS at this stage will not rewrite the boot sector of the NTFS partition which is recognised by MS-DOS 7.10 but is then totally ignored.
When booted to Windows, you'll see a drive letter has been allocated to a FAT32 partition even though you can not use that drive. You must not delete this partition - it contains your MS-DOS!
* You must recreate and copy Bootsect.dos again if the hard disk geometry is altered again.
How to return to your original Windows-only system
Remove the line C:\bootsect.dos=" MS-DOS 7.10 " from the Boot.ini file.
The only substantial change to your computer system has been the resizing and creation of the partition(s). The end of the disk is the safest area for such operations. Whenever you wish, you can reformat the MS-DOS partition with NTFS, or delete it and then resize the Windows partition to include that space.
To Format or Delete a partition, use Disk Administrator in Windows NT.
BOOT DISKS & YOUR OWN RESCUE BOOT DISK
NEVER dual-boot without your personal safety net - a BOOT DISK for XP/2K/NT.
RESCUE BOOT DISK for when XP, 2K, NT will not boot - ESSENTIAL, 1 floppy
Please remember that you alone are responsible for the consequences of any changes you make to your computer hardware or software.
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