A 2GB USB flash drive will be sufficient for most applications but you may need up to 8GB. USB Flash drive – with enough free space to hold the files of the ISO image.You will need a few things before you can get started: This article will explain step-by-step the process to make your USB Flash drive bootable and extract your ISO files to the USB flash drive. With the size and convenience of USB Flash drives you may find the need to copy boot CD ISO to USB drive.