Making a Bootable DOS USB Drive to Upgrade BIOS

   To upgrade the BIOS on my Dell Latitude E5410 I need either *.hdr files or
the Dell-supplied *.exe files. For my machine only the latter are available.
They are binary executables, not self-extracting archive files so I need to
boot the laptop into DOS in order to upgrade the BIOS.

   I downloaded FreeDOS-1.1 (fd11src.iso) and copied it onto the USB flash
drive with 'dd if=fdsrc11.iso of=/dev/sdb1 bs=1M' (as root). this produced
a couple of files and a couple of directories on the USB drive, but it's
read-only so I cannot copy the BIOS firmware .exe files to it.

   An hour or more of searching the Web found several sites that have
explicit instructions for making a bootable DOS USB drive from ubuntu (or
ubuntu-based) systems, or from Windows. I'm trying to find a way to get a
bootable DOS on the stick from my Slackware systems.

   Pointers, suggestions, advice, and recommendations greatly appreciated.

Thanks in advance,

Rich