Creating DOS floppies and USB thumbdrives for BIOS flashing

MS-DOS or another DOS derivative is still required for flashing the BIOS on some desktops, servers, notebooks, and mobile devices. These tools automate the creation of boot floppies and USB thumbdrives instead of fighting with tools like MKBT (Make Bootable).

Required Tools


  • Windows is required to run both installers. I have not tested under Wine or emulation.
  • The unofficial MS-DOS 6.22 boot floppy comes from and not from Microsoft.
  • The official Dell 32 Bit Diagnostics utility comes directly from Dell but AUTOEXEC.BAT must be modified for use on a non-Dell system. The info page for version CW1337A0 is available from Dell Support and additional versions are available directly from the Dell Diagnostics Repository.
  • Some prototype netbooks and MID devices refuse to boot MS-DOS. You’re on your own.
  • These tools are not licensed for redistribution.
  • These tools will erase the destination floppy disk or USB thumbdrive before creating bootable media.

MS-DOS 6.22 boot floppy

  1. Attach a USB floppy drive and execute BOOT622.EXE.
  2. Follow the on-screen instructions to write image to the floppy disk.
  3. Remove unneeded files to free up space and copy your custom BIOS image and BIOS flash utilities to the floppy disk.
  4. Upon booting, the floppy disk will be drive A:.

Dell 32 Bit Diagnostics

  1. Execute CW1337A0.EXE to extract archive contents to a folder.
  2. Execute DDDP.EXE and insert a USB thumbdrive.
  3. Select Install to a USB Flash Drive.
  4. Select the USB Flash Drive to use and click OK.
  5. If the USB thumbdrive is too large then a warning will be displayed regarding the maximum size of FAT 16 partitions; click Yes to continue.
  6. Click OK when complete then select Finished Creating Diagnostic Media.
  7. Modify AUTOEXEC.BAT on the newly-created USB thumbdrive and REM out or delete the DELLDIAG.COM and REBOOT.COM lines at the end of the script. DELLDIAG.COM will only run on approved Dell systems so by default the tool will give an error, exit, and reboot non-Dell systems.
  8. Copy your custom BIOS image and BIOS flash utilities to the USB thumbdrive.
  9. Upon booting, the USB thumbdrive will be drive C: and the Dell 32 Bit Diagnostics RAMDISK will be drive D:.

Booting Devices

Booting your device should be as simple as simple as Plug and Play; make sure the boot order is configured to see the USB thumbdrive, USB floppy disk, or internal floppy disk before the hard drive. Once MS-DOS loads follow the instructions that came with your BIOS image or BIOS flash utility.

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