USB memory sticks are compact, lightweight drives that are treated like small hard discs from the point of view of your computer and operating system. Because of this, they can be formatted and copied to as if you were burning an ISO, and also booted from. Knowing how to transfer the contents of an ISO image to a USB stick and boot from it is an important tool in recovering data from your computer.
Create a boot ISO from an operating system CD using your ISO extraction software. Software such as BBIE and MagicISO (see "Resources") creates a small boot ISO from a CD. Alternatively, download a pre-made bootable ISO from the Internet; such as Microsoft's Windows 7 boot ISO and the Ubuntu Linux "Live CD" ISO. Close the software when you have created your ISO.
Plug your USB memory stick into your computer. Load your boot disc creation software, such as MKBT (see "Resources") or MagicISO. Open the bootable ISO and select the USB memory stick as the drive to copy or burn to. Click the "Burn" button to transfer the data in the ISO to your memory stick. Close the software when you are done.
Restart your computer. Enter your BIOS set-up menu. How to do this varies from BIOS to BIOS, so consult the on-screen instructions during bootup. Navigate to the boot menu and select "USB" as your primary boot device. Save your changes and exit the BIOS set-up. Your computer should now restart and boot from USB.
Some boot disc creation software allows you to create multiple boot images on the same USB memory stick. This is useful both as a method of creating multiple bootable operating systems in order to troubleshoot computers, but also to test out new operating systems before deciding whether to switch over. If you wish to try this, consult your software's manual for specific details on how to create a multi-boot drive.
Older BIOS cannot boot from USB. This means that although you can create a bootable USB memory stick with software that runs on your computer, you cannot use it with your specific hardware. If you suspect your system is not low-level USB compatible, check in your BIOS set-up menu or consult your motherboard's manual for more details.