1. Restart your computer and watch for the first screen that shows up when you boot. You should see something that says "Press DEL to enter setup," or something similar. Press the noted key on your keyboard and wait for setup to start.
You should see a new screen pop up, called your BIOS. This is where you set a lot of low-level settings for your computer. Look through the options (being careful not to change anything) for a setting called "Boot Device," "Boot Order," or something similar. Select that option.
2. From the menu that pops up, choose your computer's disc drive and press Enter. If you're trying to boot from a USB drive, choose USB-HDD instead and press Enter. Depending on your BIOS, you may need to use the Page Up and Page Down keys to move your selection to the top of a list, instead.
3. Exit out of your BIOS, saving your changes. Usually, this option is under "Exit" on the main menu, or available via a keyboard shortcut listed somewhere on your screen.
4. Your computer should reboot. Make sure your CD or USB drive is in your computer. If you're prompted to "Press any key to boot from CD/DVD," do so. Your computer should boot into the CD or USB drive instead of your normal operating system.
-From
:
http://lifehacker.com/5991848/how-to-boot-from-a-cd-or-usb-drive-on-any-pc