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BOOTMGR - multi-BOOT ManaGeR

Copyright © 1997-2008 BTTR Software



The appearances of both, large hard disks, and a wide variety of operating systems, encourage users to install multiple OSes on their computers. The standard way of doing this is to create separate primary partitions on a hard disk for each OS (some OSes may support more sophisticated, non- standard solutions, like booting from extended partitions or loading from DOS command prompt via a dedicated utility). Normally, only one of the primary partitions is marked as active and can be booted. In order to boot another OS, you have to run FDISK or a similar program to select the active partition, and this is rather cumbersome.

To overcome this problem, you need to add a multi-boot feature to your system, which allows you to change the active partition and select the operating system just when you turn your PC on (or reboot it). The standard boot loader in your PC's Master Boot Record just finds the active partition and boots it. When you replace it with the BOOTMGR loader, a pseudo-graphical menu is displayed on the screen and you can select (using cursor keys) which OS you want to load. Or, if you don't press any key during some defined time, your default OS will boot.

BOOTMGR offers you also an option to boot from a floppy diskette in your A: drive. This is particularly useful if your System BIOS allows you to select the boot device (as most 486 and newer BIOSes do). With this option, you are still able to boot from a floppy without entering BIOS Setup, but don't need to care whether the floppy is removed from the drive when you want to boot from hard disk (and don't need to fear about so-called boot viruses).

If you have multiple hard disks with multiple operating systems, you can also select to boot from the other disks, but this option works differently than setting the first boot device to D: (HD2) in a typical BIOS Setup: BOOTMGR cannot transparently interchange drive numbers. (Please note that the label 'D:' has nothing to do with drive letters assigned by DOS and compatible systems.) Therefore, this option may not work with all operating systems.

For maximum compatibility with existing software, the BOOTMGR loader fits entirely in the Master Boot Record and does not occupy nor overwrite any additional disk space (unlike some other boot managers). Of course, this limited size doesn't allow defining user passwords, multiple configurations with more than four primary partitions, and other non-standard (and therefore sometimes dangerous) features.

The BOOTMGR startup menu (OS names, default OS and the time after which it boots) can be configured with the installation and configuration utility (''), which runs under DOS. Beside that, '' allows you to perform a few simple operations on partition tables: selecting the active partition, rearranging entries and changing partition identifiers (e.g., for hiding/unhiding them). In addition, you can erase all data in the initial two tracks of a disk, clearing the partition table and the boot sector of the first partition.


Screenshot #1: BOOTMGR installation and configuration utility ('') on a single-hard-disk system.
Screenshot #1: BOOTMGR installation and configuration utility ('') on a single-hard-disk system.

Screenshot #2: Older '' on a DOS/Windows 2000 dual-boot system having advanced options configured.
Screenshot #2: Older '' on a DOS/Windows 2000 dual-boot system having advanced options configured.

Screenshot #3: BOOTMGR's boot-process dialogue from the system configured on screenshot #2.
Screenshot #3: BOOTMGR's boot-process dialogue from the system configured on screenshot #2.

System requirements

For the BOOTMGR boot loader:

  • Intel i8086/88 microprocessor (or compatibles)
  • Any video adapter that is set to 80x25 text mode at boot
  • Hard disk accessible through standard BIOS INT 13h interface

For booting from partitions located beyond 8th Gbyte:

  • BIOS supporting the extended (IBM/MS) INT 13h interface

For the install/configuration utility (''):

  • Microsoft MS-DOS 3.30 (or compatibles)

Version history

18-MAR-2008 / 05-AUG-2012

  • allow hiding partitions with IDs 05 (EXT) or 0f hex (EXTLBA)


  • added missing copyright line to legal.txt
  • merged history.txt into bootmgr.txt
  • reformated 'License & Disclaimer' paragraph
  • shortened 'Technical Support' paragraph again
  • reformated license paragraph for all source code files
  • updated zip.mak


  • added 'Zap disk' function to clear two initial tracks of a disk
  • updated partition type list


  • infinite timeout option added to the boot menu
  • the bootstrap loader no longer occupies the space used by undocumented WinNT Volume Bytes, therefore compatibility with Windows NT/2K/XP is improved
  • the empty line between the title bar and boot menu has been removed to avoid (we hope) the 'which color is the selection bar?' confusion when there are only two boot menu items, and also to reduce code size
  • the installer can now restore and clear WinNT Volume Bytes
  • the generic bootstrap loader (formerly in external MBR image file STDLOAD.MBR) is now built into the installer
  • the installer displays a warning at startup when MS Windows or another multitasking environment is detected
  • hard disks are now numbered starting from 1, not from 0
  • small changes to the user interface, enhanced keyboard navigation
  • compressed executable with aPACK
  • simplified structure of sources with new Makefile
  • documentation updated, shortened 'Technical Support...' paragraph
  • added URL file


  • fixed a bug that prevented booting from partitions located beyond 8th Gbyte (thanks to Michael Andersson for reporting)
  • changed CHS/LBA selection algorithm to work reliably with large disks partitioned in NORMAL mode
  • fixed minor problem with text cursor on Hercules with some buggy system BIOSes
  • function 'Install -> Update partition table only' is now disabled when a BOOTMGR boot loader is found on disk, in order to prevent problems when the partition hiding table in the loader needs updating as well
  • function 'Restore MBR' of the installer now can be used for viewing saved MBRs without actual writing them to disk
  • function 'Save MBR' now saves original MBR, ignoring any changes made to the partition table
  • installer has a slightly different look
  • Makefiles adjusted for free Info-ZIP Zip


  • the boot loader can now dynamically hide FAT and NTFS partitions depending on OS selection; the installer and documentation modified accordingly
  • status line in the installer made longer, the messages are now more descriptive
  • other minor changes to the documentation
  • enhanced Makefiles


  • released initial public version


Binaries + Manual: (16.9 Kbytes)
Source code (The Netwide Assembler): (40.7 Kbytes)

Page last modified on 03-JUN-2018.
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