Set up DOS to dual boot WinXP

  • Thread starter Thread starter DWalker
  • Start date Start date
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DWalker

I have a working system at home running under XP Professional, and I needed
to flash the BIOS (to prepare for a faster CPU). Since I don't have a
floppy drive, I used WinFlash for the Award BIOS. It killed the system.

So, now... once I replace the motherboard... I would like to know how hard
it is to set up the computer to dual-boot Windows XP, alongside some
version of real-live, old-fashioned DOS, from the C drive -- not a floppy
disk.

I see that I have a BOOTSECT.DOS file on that computer. I also have valid,
licensed install CDs with Windows 2000 and Windows 98 SE (which are not
installed anywhere else). The DOS from the Windows 98 SE startup disk
would be fine, if I can get my computer to dual-boot with that.

I also know that you can create various DOS boot floppies from the files at
bootdisk.com, and I have access to systems with a floppy drive at work, if
that matters.

I know that if you upgrade from something older, *to* Windows XP, it's easy
to set it up for dual-boot. But my home computer already has XP Pro
installed on it, and now I want to add DOS as a dual-boot option.
Preferably without adding a floppy drive... but I can do that temporarily
if it will help.

Thanks for any advice.

David
 
You won't be able to do this if you only have a single NTFS partition which
is the Windows XP installation default. If you are starting from scratch with
a clean hard disk you could boot from an MS-DOS floppy disk and run FDISK to
remove all of the existing hard disk partitions and then create a small
MS-DOS partition on the drive and mark it as a the boot partition. Reboot
from the MS-DOS floppy disk and then use "FORMAT c: /S" to install MS-DOS on
the new partition. Now run FDISK one more time and mark the partition as not
bootable. Find an MS-DOS disk utility and use it to grab the partition boot
record from the MS-DOS partition and save it for later as BOOTSECT.DOS. If
you can't find a sector tool I can post a simple batch file that will grab
and save the partition boot sector using debug under MS-DOS.

Now when you install Windows XP it will create an NTFS partition using the
remaining space on the drive. After you've installed XP you can copy the
MS-DOS partition boot record to the root directory of the you Windows drive
and add the line C:\BOOTSEC.DOS="MS-DOS" to your boot.ini file in the
[operating systems] section.
 
Actually, it 's much simpler than that, provided you can are using a
FAT32-aware DOS such as that from Win98.

Before installing XP, use FDISK to create a FAT32 partition to hold both
operating systems. Format it, then then do <sys c:> from the floppy.

This will give you a basic bootable HD, which you can now test.

You'll propbably want to copy the other utilities from the floppy to a
suitable location perhaps C:\DOS, and adjust MSDOS.SYS so the boot process
points to this folder. (DOS without HIMEM.SYS is of very little use!) Or,
just put them into the root of C: in which case no adjustments needed.

Now install XP, and opt _not_ to convert the partition to NTFS. The XP
bootloader should automatically create options for both OS's. It will call
the DOS option "Microsoft Windows" -because this version mostly gets used to
load Win9x. You can change this label in BOOT.INI if you want.

Only proviso is that FAT32 partitions of over 128GB are very inefficient in
space usage (32GB is the max recommended size) so if you have a large HD you
may want to keep the sytem partition smallish and use a separate NTFS data
partition. (always a good practice anyway, IMHO.) Once booted you can access
the data in the NTFS partition with NTFSDOS, BTW.
 
Actually, it 's much simpler than that, provided you can are using a
FAT32-aware DOS such as that from Win98.

Before installing XP,
Click to expand...

XP is already installed, and has been for a long time.
...use FDISK to create a FAT32 partition to hold
both operating systems. Format it, then then do <sys c:> from the
floppy.

This will give you a basic bootable HD, which you can now test.

You'll propbably want to copy the other utilities from the floppy to a
suitable location perhaps C:\DOS, and adjust MSDOS.SYS so the boot
process points to this folder. (DOS without HIMEM.SYS is of very
little use!) Or, just put them into the root of C: in which case no
adjustments needed.

Now install XP, and opt _not_ to convert the partition to NTFS. The XP
bootloader should automatically create options for both OS's. It will
call the DOS option "Microsoft Windows" -because this version mostly
gets used to load Win9x. You can change this label in BOOT.INI if you
want.

Only proviso is that FAT32 partitions of over 128GB are very
inefficient in space usage (32GB is the max recommended size) so if
you have a large HD you may want to keep the sytem partition smallish
and use a separate NTFS data partition. (always a good practice
anyway, IMHO.) Once booted you can access the data in the NTFS
partition with NTFSDOS, BTW.
Click to expand...

I thought about all of this, but I have had XP installed for a long
time.

David
 
You won't be able to do this if you only have a single NTFS partition
which is the Windows XP installation default.
Click to expand...

I meant to mention this, but I didn't... my XP installation has a FAT32
C drive, and some very large NTFS drives to hold data and backup data.
If you are starting from
scratch with a clean hard disk you could boot from an MS-DOS floppy
disk and run FDISK to remove all of the existing hard disk partitions
and then create a small MS-DOS partition on the drive and mark it as a
the boot partition. Reboot from the MS-DOS floppy disk and then use
"FORMAT c: /S" to install MS-DOS on the new partition. Now run FDISK
one more time and mark the partition as not bootable. Find an MS-DOS
disk utility and use it to grab the partition boot record from the
MS-DOS partition and save it for later as BOOTSECT.DOS. If you can't
find a sector tool I can post a simple batch file that will grab and
save the partition boot sector using debug under MS-DOS.

Now when you install Windows XP it will create an NTFS partition using
the remaining space on the drive. After you've installed XP you can
copy the MS-DOS partition boot record to the root directory of the you
Windows drive and add the line C:\BOOTSEC.DOS="MS-DOS" to your
boot.ini file in the [operating systems] section.
Click to expand...

Can I just add C:\DOS\BOOTSEC.DOS="MS-DOS" to the FAT32 partition that
has my Windows XP installation on it, and put all of the DOS files
there? I suppose I can try this without much danger.

David
 
DWalker said:
Can I just add C:\DOS\BOOTSEC.DOS="MS-DOS" to the FAT32 partition that
has my Windows XP installation on it, and put all of the DOS files
there? I suppose I can try this without much danger.
Click to expand...

This will only work if the file C:\DOS\BOOTSEC.DOS file is actually located
in the C:\DOS directory and the file contains a valid MS-DOS partition boot
record that matches the C: hard drive partition.

The line C:\DOS\BOOTSEC.DOS="MS-DOS" tells NTLOADER to read the file
C:\DOS\BOOTSEC.DOS into memory for execution and the file must have the
existing C: partition layout correctly set within the file or else when it
executes it won't be able to find the MS-DOS file located on the partition.

You would also need to place the MS-DOS system files in the root directory
of the C: drive.
 
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