If you want to install a new operating system from a CD/DVD, or to run a Live OS, or maybe want to use recovery tools from USB/Floppy disk drive you'll need to configure the BIOS boot order/sequence first.

In order to perform this action follows these steps:

1. Enter to the motherboard BIOS, in order to do that check in the screen when you start up the computer for small line in the POST (Power On Self Test) screen.

Most of the motherboards manufacturers provide a small line like this: "Press X to run Setup" or "Press X to enter BIOS setup" when X is the specific key that enable you to enter the BIOS. Most of the motherboards use Delete (Del)/F2/F10/Ctrl+Alt+Esc in order to enter to the BIOS setup.

If you still didn't find the correct key, check your motherboard user manual.

2. When you entering the BIOS go to the Boot tab, or look for Advanced BIOS Features, (most of the BIOS vendors provide one of these options).

3. Then look for the Boot Device Priority or for First, Second and Third Boot Devices. And with the +/- or Enter keys change the order of the boot.

Note: If you want to boot first from your CD/DVD drive, and then set the first boot device to your CD/DVD drive, the rest isn't matter because first you want to boot from CD/DVD. If you want to boot the system faster set the first boot device to your local hard disk drive.

There's also a well-known BIOS vendors that provides specific hardware detection by manufacturer and model name, and provide ability to identify the correct device in the boot sequence.

4. After the changes, save the settings and exit BIOS. Most of the BIOS vendors provide you a simple way to do this by using the F10 key.