How to create a Dos Bootable USB Stick?
Download a tool called BootFlashDos from the link below:
Run the downloaded file BootFlashDos.exe
Insert the USB stick onto one of the USB ports where the application is running.
Click on the checkbox Quick Format.
Click on Start to make the USB key a dos bootable media.
Note: Some USB key comes with software already on it; you will need to remove the software in order to make it work. Otherwise, it is best to use another USB key.