Updating your BIOS from a FreeDOS Bootable USB

Tutorial Video

This guide will first show how to prepare a FreeDOS Bootable USB within Windows using Rufus and use it to Update the BIOS. It will then go through making a FreeDOS Bootable USB within Linux Ubuntu using Unetbootin and use it to Update the BIOS.

Creating a FreeDOS Bootable USB with Rufus (Windows 10)

To check your BIOS version within Windows, press [Windows] and [ r ] and type in msinfo32

Here we see that this is a Dell OptiPlex 790 at BIOS Version A15:

All BIOS Updates for Dell models are available at:

Selecting OptiPlex 790, and thenBIOS I can see that my latest Update is A22:

I will save A22:

Next we will need to Download Rufus. Rufus is available here:

Launch Rufus and accept the User Account Control:

You do not need to check for updates, immediately after downloading the latest version:

Insert your USB Flash Drive. I am going to use an old 2 GB USB Flash Drive:

Under Boot Selection select FreeDOS:

The Partition Scheme and File System are MBR and FAT, leave these as is. FreeDOS doesn’t support a UEFI Boot with Secure Boot so these will need to be temporary Disabled in the UEFI BIOS Setup to Boot from the FreeDOS Bootable USB:

You can change the Volume Label (optional):

When ready, select Start:

You will get a warning stating you will loose all your data on your USB. Select OK:

When Rufus is done, it will say Ready, you can close Rufus now:

Now find your BIOS Update:

Right click it and select Copy:

Go to your FreeDOS Bootable USB:

Paste the BIOS Update:

Your FreeDOS Bootable USB is now ready:

Updating your BIOS Using the Rufus FreeDos Bootable USB

Note if you have a system with a UEFI Boot with Secure Boot, you will need to temporary Disable it and allow a Legacy Boot with Legacy ROMs Enabled.

This OptiPlex 790 has an early UEFI BIOS so it always has both a Legacy and UEFI Boot option listed. In this case Legacy ROMs are always Enabled and this system does not have Secure Boot.

Power up your system with the FreeDOS Bootable USB and press [F12] to get to the Boot Menu:

Press the [↓] key until you get to your USB Flash Drive. If you have a system with a UEFI BIOS, you should select the Option under Legacy Boot:

When you have selected your USB Flash Drive, press [Enter]:

You will be given an option to select your keyboard layout. I will select UK-English:

You will now get a FreeDOS console:

Type in

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This will list all the files on the USB Flash Drive:

The BIOS Update should show. In this case O790-A22

Type in the name of your BIOS Update followed by .EXE in my case:

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You will get a Dell warning about Updating your BIOS, basically informing you that the loss of power (or force shutdown) during the BIOS Update may brick your system. Press:

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To proceed:

Now it will tell you the Version Installed and the Version Available to Update:

Once again press:

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To proceed:

The BIOS Update will now begin:

The system should automatically reboot when the update is complete:

It now says A22 so the BIOS Update is complete:

The version can also be checked within Windows by pressing [Windows] and [ r ] and type in msinfo32 and press [Enter]:

It is A22 as expected:

Creating a FreeDOS Bootable USB with Unetbootin (Ubuntu)

Insert your USB Flash Drive and search for Disks. Launch Disks:

Select your USB Flash Drive and check what device it is, in this case /dev/sdb1

Search for terminal:

Copy and paste the following commands into terminal:

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Enter your password when prompted:

Press Enter

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Press y to proceed:

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And finally to launch Unetbootin input:

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Under distribution select FreeDOS:

Under Device select your device, in my case/dev/sdb1

All data on your USB Flash Drive will be wiped. Select OK:

Press [Exit]

You now have your FreeDOS Bootable USB Flash Drive:

All Dell BIOS Updates are available at:

Select your Model and then BIOS, download the latest BIOS Update for your model:

Save the file:

Copy it over to your FreeDOS Bootable USB:

Updating your BIOS Using the Unetbootin FreeDOS Bootable USB

Note if you have a system with a UEFI Boot with Secure Boot, you will need to temporary Disable it and allow a Legacy Boot with Legacy ROMs Enabled.

This OptiPlex 790 has an early UEFI BIOS so it always has both a Legacy and UEFI Boot option listed. In this case Legacy ROMs are always Enabled and this system does not have Secure Boot.

Power up your system with the FreeDOS Bootable USB and press [F12] to get to the Boot Menu:

Press the [↓] key until you get to your USB Flash Drive. If you have a system with a UEFI BIOS, you should select the Option under Legacy Boot:

When you have selected your USB Flash Drive, press [Enter]:

It will Boot Using Default:

In the next screen press the [↓] key to get to FreeDOS Safe Mode:

Press [Enter]:

Unlike the Bootable USB created with Rufus, this Bootable USB starts in A:\ and not in C:\. Type in:

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Type in:

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To list all the files on the Bootable USB:

Your BIOS Update, in my case O790-A22.EXE should be listed to launch it type in its name followed by .EXE:

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Follow the onscreen instructions to perform the BIOS Update, as this system has just been updated via the Rufus FreeDOS Bootable USB I will press n to cancel the update.

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