
DOSTOWXP.COM is a freeware loader, which enables to use MS-DOS7.10
 as a boot manager for launching a pre-installed Windows-XP OS.

Submitted example of DOSTOWXP.COM is a preliminary trial version.
 It is provided "as is", without guarantees of any kind. You may use
 it exclusively at your own risk. The author claims no responsibility
 for any possible damage, which may be inflicted on your property
 because of your experiments with DOSTOWXP.COM loader.

DOSTOWXP.ZIP archive includes the following files:
    CONFIG.SYS   - example of DOS configuration file;
    DOSTOWXP.COM - a trial example of the loader file;
    DOSTOWXP.SCR - command file for debugger DEBUG.EXE;
    README_E.TXT - this README file;
    TEMPLATE.DAT - boot sector data file.

First impetus to arrange a DOS loader for Windows-XP was a desire
 to find out the causes of booting failures, which are not disclosed
 by Windows-XP itself. Idea started as a number of checks in DOS
 operating environment, enabling to get some comprehensive message
 and to take appropriate measures just afterwards, without reboot.
 Later an opportunity to initiate Windows-XP launching has become
 evident, was implemented and was found convenient.

As far as DOS can't cope with NTFS volumes, DOSTOWXP.COM implies
 presence of a HDD's active primary partition, formatted as FAT32.
 Preferably Windows-XP should be installed in some non-primary NTFS
 partition of the same disk. MS-DOS7 may be either installed in the
 mentioned active primary partition or launched from other media:
 a floppy, an optical disc or solid-state storage device. Your first
 important decision must be whether you can afford experiments
 concerning DOSTOWXP.COM loader with regard to particular partition
 structure of your HDD.

If HDD's partition structure is suitable, DOSTOWXP.COM should be copied
 into root directory of active primary partition. For the first time
 it's better to launch the required DOS operating environment from
 external media, but this external media must not be registered by
 BIOS as disk C:. Registration of an external media as disk C: shifts
 numeration of physical HDDs and makes NTLDR unable to find proper
 system data. Hence you may launch MS-DOS7 from an external media,
 but this media must either be a floppy, or be formatted as a floppy,
 or be emulated by BIOS as "Forced FDD".

An important requirement to operating environment is that CPU must stay
 in real mode. Therefore EMM386.EXE driver must not be installed before
 execution of DOSTOWXP.COM. Access beyond conventional memory area in
 real mode may be provided by HIMEM.SYS and UMBPCI.SYS drivers. The
 latter can be downloaded from internet site http://www.uwe-sieber.de.

In HDD's root directory DOSTOWXP.COM may be executed as an ordinary DOS
 utility. DOSTOWXP.COM makes necessary preparations, checks presence of
 NTLDR and BOOT.INI system files, and then transfers control to NTLDR.
 DOSTOWXP.COM is able to initiate launching of Windows-XP OS even when
 Windows-XP can't start normally due to damaged boot sector code in HDD's
 active partition. If something goes wrong, DOSTOWXP.COM doesn't initiate
 reboot, but rather displays an error message and returns control to DOS.
 In any case DOSTOWXP.COM doesn't attempt to access HDD's boot sector and
 leaves it intact.

As far as DOSTOWXP.COM doesn't rely on boot sector code in HDD's active
 partition, this boot sector code, originally written by Windows-XP,
 can be more than damaged - it can be intentionally replaced by some
 other boot sector code, in particular, by the one of MS-DOS7. Hence
 MS-DOS7 can be installed into HDD's active partition and will play
 the role of boot manager for Windows-XP. Of course, experiments with
 boot sector shouldn't be commenced unless original boot sector is
 copied into a file and saved. Copying and restoration of a boot sector
 may be performed, for example, by DISKEDIT utility, supplied in NORTON
 UTILITIES software release.

Standard DOS's boot sector is most often formed by SYS.COM utility.
 Then you have to copy MS-DOS7 files according to chosen directory
 structure. System files of MS-DOS7 (IO.SYS, MSDOS.SYS, COMMAND.COM)
 together with CONFIG.SYS, AUTOEXEC.BAT and DOSTOWXP.COM files must
 be written into the root directory of active primary partition.
 DOSTOWXP.ZIP archive includes an example of CONFIG.SYS file with
 simple boot menu, enabling to choose launching of either Windows-XP
 or MS-DOS7. If DOSTOWXP.COM has to be executed exclusively inside
 a separate boot menu item, then other boot menu items may specify
 configurations with switching CPU into V86 mode.

Those interested may find some details of DOSTOWXP.COM composition
 from commentaries in lines of DOSTOWXP.SCR file. The author had no
 opportunity to test DOSTOWXP.COM loader troughout the whole variety
 of possible circumstances. Most probably the first trial version
 of DOSTOWXP.COM loader is not free from bugs and some drawbacks.
 If you are ready to make corrections in DOSTOWXP.SCR command file,
 then DOSTOWXP.COM loader should be re-assembled with command:
              DEBUG.EXE TEMPLATE.DAT < DOSTOWXP.SCR

The author will be grateful for your participation in testing
 DOSTOWXP.COM loader and especially for relevant remarks concerning
 its further enhancement.

Nickolay G. Hitrovo
23.04.2008. E-mail address: For-H@yandex.ru


