USB flash drives have become a popular method of storing data in a small, easily transferred format. Unlike the floppy disc they have now superseded, USB drives are durable and therefore a more viable option for the creation of emergency boot discs. Knowing how to make a bootable ISO on a USB flash drive is therefore an essential skill in data protection and recovery.
Create or download an ISO of a boot disc for the operating system of your choice. Bootable images for Linux and Windows recovery disc images are widely available on the Internet. Some popular choices are the Windows 7 ISO from Microsoft, or the Ubuntu Linux "Live CD" ISO. After the download, open the image in your ISO extraction software, such as MagicISO or BBIE.
Extract the boot sector information from your ISO using your ISO extraction software. If you use BBIE, enter "bbie isofilename" at the command prompt to extract the boot image. If you use MagicISO or equivalent software with a graphical interface, click its "Export boot image" option when burning an image. Close the software.
Open your boot disc creation software, such as mkbt or MagicISO. Select the USB drive to burn the bootable ISO to it and click "Burn." Wait for the boot information to be copied to the USB drive. Close the software. Reboot your computer and enter your BIOS boot menu. Select "USB" booting, if you have not already done so, then save your changes. Exit your BIOS menu to restart your computer and boot from USB.
If you require multiple boot options, consider setting the "master boot record" on your USB drive to point to different portions of the drive, each of which contains information on a different operating system. This will allow you to boot multiple operating systems from one USB drive; which is useful for troubleshooting your system. Follow the instructions for your boot disc creation software for specific instructions on how to do this.
In order to boot from a USB flash drive, your computer's BIOS must be USB boot compatible. Older systems do not recognise USB at a low enough level to be able to boot from it. To check your BIOS compatibility, consult your motherboard's manual, check the manufacturer's website, or boot into your BIOS set-up menu and see whether you can select "USB" as a boot option.