Howto: BIOS-Update per bootable CD

BIOS Boot-CD - Howto: BIOS-Update per bootable CD


A guidance how to create a Boot-CD (MS-DOS v6.22) to perform a BIOS update.

see also: BIOS-Update Howto: step-by-step instruction
see also: BIOS Update per bootable USB-Stick
see also: BIOS Update per DOS-Boot-Diskette


Important: this method simulates/emulates a floppy drive. Due to the size limitation of a 2.88MB floppy disk, you can only use a BIOS file and flashtool whose total file size is max ~2.7MB!

Recommendation: i prefer to use the method BIOS Update per bootable USB-Stick!
A bootable pendrive has no size restrictions and more importantly: you can create a BACKUP before updating the BIOS - and that's always a good idea!


The following tools are needed:

  • CDBurnerXP - free CD-Burning software, Download from manufacturer's website
    Attention: download the CDBurnerXP-Version without OpenCandy or installCore! (Adware!)
  • UltraISO - Trial version, Download from manufacturer's website
  • Ultimate BIOS-Boot-Edition:
    - msdos.img (the boot image contains only the most important MS-DOS operating system files)
    DOWNLOAD Ultimate BIOS-Boot-Edition - 1.2MB
  • Flashtool - BIOS-Programming-Software (.EXE as file extension), which programs the BIOS file onto the BIOS-Chip, and the BIOS file. Both files must be downloaded:
    - Mainboard, bought in its original box: from the mainboard manufacturer website, or
    - Notebook or brand PC: from the notebook/brand PC manufacturer website.
    Both files must be specially designed for the DOS Operation system! If the manufacturer offers only files for Windows, you have to risk the BIOS update either directly under Windows, or you can re-program your old BIOS-Chip, or purchase a new, programmed BIOS-Chip.


New BIOS-Chips (incl. programming) --> in my Shop


Instruction to create a bootable CD

  • Tip: use - if possible - a rewritable CD-RW.
  • Open the Ultimate BIOS-Boot-Edition and extract the boot image file (folder boot_cd) msdos.img.
  • Install and start the Trial version of UltraISO.
  • Open the boot image file msdos.img with UltraISO.
  • Rename the filename of your flashtool and the BIOS file, if they have more than 8 characters (not the file extension!).
  • Copy the flashtool and BIOS file (with Drag&Drop) to the other existing files (see picture).
  • Save the boot image file and close UltraISO.
  • Start CDBurnerXP and choose Data disc:
  • Create the text file dummy.txt with any content (1 byte is enough) and drag&drop it to the compilation. (Reason: CDBurnerXP cannot successfully create a CD if there is no file in the compilation)
  • In the CDBurnerXP main menu Disc choose the entry Boot options...
  • In the following window (see picture) enable the checkbox Make disc bootable and insert the path to your boot image file msdos.img.
  • Change the Emulation type to Floppy 2.88MB.
  • Click the OK-Button to close this window.
  • Now you can use Ctrl+B to burn the CD.
The DOS system files are normally invisible, because their file attribute is set to hidden. If you would like to show these hidden files, you have to enable the option: "Windows-Explorer / Tools / Folder options / View / Show hidden files and folders" and to disable the option "Hide protected operating system files".


Starting the BIOS-Update from CD-ROM

  • First, go into your BIOS-Setup and change the Bootsequence to CD-ROM (search for an option like Bootsequence, First Boot Device, or something similarly).

  • Insert the CD and restart your PC. If all went well - MS-DOS starts and you can see the famous DOS-Prompt (A:\>).

  • Now you can start the BIOS update, but remember: you can't backup your old BIOS version onto a CD! But if your harddisk has a FAT16- or FAT32 partition, it would be a good idea to copy your 2 BIOS files to this partition, and to start the update/backup from your harddisk.

  • See also: BIOS-Update Howto: step-by-step instruction

Happy flashing!

User-Comments: BIOS Boot-CD
David 5.Oct.2012 20:15

Worked all the way! thank you so much!

biosflash 1.Nov.2011 15:12

@Heinrich Giersch Das geht leider nicht so ohne weiteres bei Notebooks. Siehe

Heinrich Giersch 1.Nov.2011 13:11

Sehr geehrte Damen und Herren, ich bin wenig hilflos! Ich moechte gerne mein BIOS-Passwort aendern. Wie kann ich dies machen? Mein Nootebok hat die folgende Konfiguration. Asus A42J mit einer ca. 320 GB Festplatte und 4 GB Memory, desweiteren hat mein Computer Wireless LAN Software ist Installiert, Windows 7 Ultimate Mit freundlichen Gruessen Heinrich Giersch PS.: Es ist sehr gut, diese Hilfe im Internet.

biosflash 21.Jul.2011 06:19

use the other method: "BIOS Boot-CD II", or better: try to make the BIOS Update per bootable USB-Stick.

sul 21.Jul.2011 04:29

so what do you do if your bios update file is 4megs? i cant add the bios file because the drdosmin.img only allows 1.44megs like a floppy.

srimal 16.Jul.2011 07:50

this is good web page in internet

Elric 3.Jul.2011 02:44

This is ecxatly what I was looking for. Thanks for writing!

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