Some programs and operating systems are designed to be booted, or started, from a USB device. Most computers are capable of booting from USB; however, a quick change to the computer's BIOS is often required to allow such a boot. Manually enabling USB booting in the computer's Basic Input Output System (BIOS) may be required, as computers are typically set up to first boot from the hard drive. After enabling USB booting, changing the standard boot device order may also need to be done in the computer's BIOS settings.
Plug the USB drive into a running computer and open its folder from the "My Computer" folder to check for file format type. Verify that the USB drive contains a bootable program; bootable programs are usually in the file format .ISO or .BIN. A file should be in the main folder of the USB drive ending in one of the above file types, or another known bootable file type. If the program is in a sub-folder, moving it to the main folder may enable its booting.
Enter the computer's BIOS program. On most computers, do this by pressing the "F2" key immediately after powering the computer on. Some models require the "F1" key or the "Delete" key, thought most indicate which key controls BIOS at the start-up screen. Using your keyboard, scroll to the boot options in the BIOS and select "Enable USB Boot." This option may be phrased differently depending on the computer model and manufacturer.
Change the boot order of your computer using the settings in the BIOS. The boot order priority menu allows you to move devices and drives in a list of bootable devices, indicating which device you want to boot from first. If the device is missing or not able to boot, the computer will use the next device in the list. To temporarily change the boot order on most computers, press the "F6" key after powering the computer on, before the operating system loads.
On computers that do not automatically show file extension type, it may be necessary to manually set file extensions to be shown. Click "Folder Options" on the menu bar of any folder, under the category "Tools." Select the option to show file extensions and click "Save Settings."