Modifying FreeDOS Installation ISO for Updating BIOS

There are some older computers that still need the good old DOS operating system to update the BIOS. These computers actually show a prompt to insert the 1.4′ floppy disk when you choose to update the BIOS using one of the options at the computer startup. But nobody has floppy disks anymore or and many have never heard of MS-DOS either. Both of these have gone the way of dodo bird. But you can still manage to update the BIOS on these legacy systems using a modified bootable FreeDOS CD. Here is how:

  1. Download the FreeDOS 1.0 CD ISO image from The reason we download an older version of FreeDOS is because it is easy to modify.
  2. Download PowerISO and install it in your PC. It tries to install unwanted software (PUP), but you can avoid the unwanted programs by turning off the internet (turn off WiFi or pull Ethernet cable) during installing.
  3. Download and install 7-Zip in your PC. This is used to extract files from the ISO image.
  4. Download and install Notepad++. This will be used to edit some files.
  5. Right-click on the downloaded ISO image (step #1) and choose 7-Zip → Open Archive. When the ISO image opens in 7-Zip, extract setup.bat from it to somewhere on your hard drive.FreeDOS BIOS Update CD
  6. Open the extracted file setup.bat in Notepad++. Add goto end line after the set fdosroot=%_CWD%FreeDOS\Setup line in this file and then save this file.FreeDOS BIOS Update CD
  7. Open the ISO image in PowerISO, drag-and-drop the edited setup.bat file into PowerISO window and choose to overwrite the file.
  8. Similarly, drag-and-drop other programs (like the BIOS update program) and other programs in the FreeDOS folder in the PowerISO window. Finally click on the Save button.FreeDOS BIOS Update CD
  9. Now you can burn this ISO image to a blank CD by clicking on the Burn button in PowerISO.

When you boot using this CD, you will have to press 1 to continue booting from the CD. And then when you choose the default install option, the installation won’t start. You can switch to the FreeDOS directory using the CD freedos command and then go on to execute your own programs like the BIOS update or games or anything else.

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