DOS Bootable USB flash drive - how I did it

    There are 2 things you need in order to make an USB flash drive boot into DOS. The first is a boot sector, and the second are the DOS boot files. Below are the steps I used to get these onto a USB flash drive, making it possible to boot into DOS from the USB flash drive.

    The following steps where all done in Microsoft Windows XP in a VMware virtual machine. They should work with most other versions of MS Windows. I successfully used these steps on an USB flash drive I got at Immersion Week 2008 for use in a ZFS demo (Identifies itself as CBM). YMMV depending on USB flash drive model and manufacturer. These steps are based off of the very useful information at

1) Getting a boot sector on the USB flash drive
    Start by gettng the mkbt DOS utility from here mkbt
    Unzip mkbt into a temporary directory
    OK, if you are like most people these days, you don't have a floppy drive in your laptop or desktop, and you may never have, although you should know what a floppy is if you have any interest in doing this. So, if you don't have a floppy drive in your machine, you can use vfd to create a virtual floppy, which is what I did. You can get vfd from here vfd, then follow the directions for creating a virtual drive in RAM, then save it as a file for future use. Use the Windows Explorer format menu item to format the virtual floppy and make sure you check off the box to make an MS-DOS start up disk.

    Once you have access to a DOS boot floppy, use the following command, from a command prompt, to save the boot sector, where a: is the drive letter of your DOS bootable floppy (virtual or physical)

mkbt -c a: bootsect.bin

    Now use the following command to write the boot sector to your USB flash drive, where n: should be replaced with the drive letter of you USB flash drive.

mkbt -x bootsect.bin n:

2) Getting the DOS boot files
    copy all the files from the boot floppy onto the USB flash drive.

    Now you should have a DOS bootable USB flash drive, for use with a system that supports booting from USB, including x64 products from Sun. Copy over whatever DOS utilities you need to use, including AFU for Adaptec RAID controller firmware updates, which is used in some of Sun's x64 products. Or use it for whatever need you may have. Even with a small USB flash drive, you will have a lot more room than a floppy ever dreamed of. Perhaps my next blog post should be on whether inanimate objects dream. :-)

Update : Per several comment poster's, I have fixed the command line for writing the boot sector onto the USB flash drive. It is now correct in the above post. Thanks to those who caught my mistake. :-)

i have done everything, but still when I try to boot from my flash drive (4GB Imation) it says "No bootable partition in table". Could You plese advise me what to do?

Posted by Petar Milev on July 16, 2008 at 10:22 PM EDT #


I'll start by saying that it has been my experience that not all USB flash devices are created equal, so there are no guarantees that a particular model can be made bootable. Did you encounter any messages, error or otherwise, during the steps, particularly step 1? One of the things I did not mention is that my USB stick was formatted with a FAT file system, so if your USB device has been formatted with some other file system, that could explain your problem.


Posted by Perley Mears on July 19, 2008 at 04:42 AM EDT #


Posted by tejas jani on September 11, 2008 at 01:33 AM EDT #

i tried all above given statement, on first command, it creates bootsec.bin file in the folder i created. But the second command.

mkbt -x H: bootsec.bin
it gives message like

\* expert monde (-x)
\* warning different filesystem Id
Size=0bytes oem="vfd2.1" vollabe-"no Name" filesys-"fat12"

ever i formated the flash drive with fat.



Posted by yasin on November 28, 2008 at 08:32 PM EST #


Posted by DONNY51972 on January 11, 2009 at 02:11 AM EST #

Another method:

Download and install WinSetupFromUSB0.1.1. Run app.
Select HP Format Tool
Format Options - Create a DOS Startup Disk, using DOS system files located at:

I pointed the path to a USB FDD which had a dos 6.22 boot disk inserted. Whola!

This creates a USB Boot stick with only, IO.sys and MSDOS.sys. I used this on a SUN Server so I could upgrade the Firmware on a PCIe Qlogic HBA.

Posted by Brad on January 20, 2009 at 04:36 PM EST #

No wonder it did not work for tejas jani.
This command is plain incorrect:

mkbt -x n: bootsect.bin

It has to be mkbt -x bootsect.bin n .

I myself spent a lot of time trying to figure out what's going on until I found it here:

Posted by Victor on March 07, 2009 at 01:26 PM EST #

The command is mkbt -x bootsect.bin n:

I found however that when I tried to run this command using the letter of my usb key (m:) I kept getting an Invalid Handle message.

I tried it without the usb key in again using m: and it gave me the same error.

This lead me to think that it was not recognising the drive letter for some reason.

I then copied mkbt.exe and bootsect.bin to the m: drive via windows explorer and then through a cmd prompt switched to m: and then ran the mkbt -x bootsect.bin m: command and it ran fine giving me the expected warning about different file system.

Copied my IO.SYS and other files across rebooted and it worked just fine.

Posted by Nix on April 01, 2009 at 01:09 PM EDT #

I may have a clue on what is going on: depending on the size of the flash card, a different FAT standard applies (FAT12, FAT32) and in some cases the formatting tool may be creating a partition, in which case the first sector of the volume would contain a partition table instead of the boot sector. Try using a card of less than 4GB to see if it works.

Posted by Miguel Dutra on October 23, 2009 at 09:59 AM EDT #

Dear Dragonfly,

I can only say, thanks God that you posted this information. It worked well and I could go asleep at 2 o'clock at night, after I have had hours of trying other shit before. OOOH, why didn't I find your posting earlier??


Posted by Bernd on December 03, 2009 at 08:35 AM EST #

Hi , i got this to work but the only problem i had was that you did not state in your (How To) that I needed to be in the same directory as extracted files before before executing commands, apart from that it worked after some messing about on my part here.

Thanks for mkbt.


Posted by bruce on December 24, 2009 at 04:44 PM EST #

So, you say that simply copying IO.SYS and MSDOS.SYS after boot sector transfer can make drive bootable... Well, as I can remember, moving IO.SYS to other sectors on a floppy always caused the floppy to loose its booting feature as the boot sector must know in which sectors IO.SYS located is. Anyway, I didn't manage to make my USB drive bootable. I can see that the boot sector reached its destination, but when I attempt to boot, it simply boots from HDD although BIOS setting is set to boot from USB drive (so do two independent computers). May it be that my USB drive (actually a SD card reader) does not support booting?

Posted by Paul on January 30, 2010 at 03:57 AM EST #

I need DOS Bootable flash

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Thanks for this tip, I was great headache for me before read your post. but you solved my problem, thanks again.

Posted by Rakesh Solanki on March 07, 2010 at 02:47 AM EST #

Hi , i got this to work but the only problem i had was that you did not state in your (How To) that I needed to be in the same directory as extracted files before before executing commands, apart from that it worked after some messing about on my part here.

Posted by replica pandora jewelry on March 09, 2010 at 06:34 PM EST #

Nice post.
Usefull for messing about with different Windows installs....

Long gone are the floppy days haha.

Posted by Simple Hosting on March 16, 2010 at 09:26 AM EDT #

Hello all, Is any one still watching this thread? I cannot get this to work. I end up with an "Error cannot load operating system." Works fine every time with the HP utility and the same floppy image.

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Posted by UK GHD on July 19, 2010 at 10:22 PM EDT #

Hi im having trouble. Could you maybe talk me though it (in the response to this comment) im not sure i made the VFD right, and i just put mkbt into a regular folder. I can't figure out how to format the vfd into a MS-DOS startup disk. A quick response would be greatly appreciated.

Posted by NICK on August 22, 2010 at 04:01 AM EDT #

Worked perfectly

Posted by Richard on August 31, 2010 at 05:31 AM EDT #

When using WinSetupFromUsb and are going to format your usb. Do NOT check the "make it a dos startup blabla"!

Posted by Sarah James Pedelson on September 02, 2010 at 06:02 AM EDT #

seems so much simpler

Posted by RayRay on January 21, 2011 at 03:28 AM EST #

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