Computer boot order

Some actions require that you boot (this means "start") your computer from a CD/DVD or a USB drive. For example, when Windows does not start properly, or when you need to check if your computer random access memory (RAM) is working fine.

Most modern computers are set to boot from CD or DVD first, and if there is no bootable media in CD or DVD drive then from the first hard disk.

To boot from a CD/DVD or a USB drive, you must insert or connect the media first and then restart or turn on your computer.

Using boot menus for one-time boot device selection

On some computers you can select your boot device without entering BIOS/UEFI by pressing F8 key before Windows (or any other operating system) starts, but most common ones are F9 on HP, F10 on Sony, F11 on MSI, F12 on Lenovo, Dell and Acer, and ESC on ASUS.

Let's see some examples of quick boot selection options.

Dell computers always display the "F12 Boot Options" message on top right of screen for a few seconds, so you have to act quick and press the F12 key. Pressing it more than once does not hurt.

Now you can use arrow keys to navigate in the menu and press Enter to boot your PC from the selected device.
Please note that you have to plug in your USB stick or drive before restarting or turning on your PC to see the USB Storage Device option. This applies to all computers, not only Dells.

And here is an example of a desktop computer with MSI motherboard. Boot menu keyboard shortcut is listed on bottom right for a few seconds, so press F11 to select a temporary boot device.

Again, use arrow keys to navigate and press Enter to confirm your choice.

Changing boot order in BIOS or UEFI

You have to use a system setup utility to change boot order permanently. The utility is most often called BIOS (Basic Input/Output System) setup or CMOS (Complementary Metal-Oxide-Semiconductor) setup, or Setup Configuration Utility/SCU.
Most modern PC-s have a BIOS alternative called EFI (Extensible Firmware Interface) or UEFI (Unified Extensible Firmware Interface).

You can access the setup utility by pressing one or more keys on your keyboard before your operating system (Windows, Linux, etc) starts. As there are very many different computer manufacturers, these keys or combinations are different, but they are almost always displayed on screen. These shortcut keys are also in the manual that came with your computer.

Most usual keys are F1, F2, F10, F12 and Del (aka Delete). On some computers you might have to press Esc key first to see options list.

Please do not change any other settings than boot order! BIOS/UEFI setup utility is a very powerful program and you can make your computer inoperable when you mess around with it!

Let's see some examples again.

Example one - Dell laptops

Dell does not display BIOS/UEFI access key at startup, so press F2 key several times while Dell logo is displayed.

Expand General section from the top left and click Boot Sequence. Arrow keys and Enter work as well. In the Boot Sequence section, you can tick or untick device types to enable or disable booting from these. To change device priority, click its entry on the right so that the item becomes highlighted (changes to blue) and then use Up and Down buttons or PgUp and PgDn keys to move the entry up or down in the list. Finally, click Apply in the bottom of the screen.

Here's another Dell example, but from an older Latitude D630. Boot Sequence is in System section. Use arrow keys to navigate and Space to enable or disable a device type. To change a device type priority, use U and D keys for moving the item up or down. Finally, press Enter to confirm changes.

Example two - MSI desktop

Back to the computer with MSI motherboard. As shown on the startup screen, you need to press Del key to access BIOS setup.

This motherboard has full UEFI support, so you can quickly change boot order just by dragging the device type icons on top of the screen. Icons with letter "U" indicate UEFI boot order, others are for legacy/BIOS boot order.

You can also do this the old-fashioned way, just click Settings on the left (see screenshot above) and then click Boot in the Settings list.
Here you can use arrow keys to navigate, Enter key to choose an item and +/- keys to move the chosen item up or down in the list. Press Esc key after you are done, and then choose Save & Exit from the Settings list.

Example three - Gigabyte desktop

Here's an older desktop PC with Gigabyte motherboard.
To change boot order permanently, you will have to press Del key on your keyboard to access BIOS setup.

Use arrow down key to select Advanced BIOS Features, then press Enter key once.

As you can see, First Boot Device is CDROM, Second Boot Device is Floppy and Third Boot Device is Hard Disk. Use arrow keys to navigate and press Enter to select an item. Then use + and -, or PgUp and PgDn keys (short for Page Up and Page Down keys) to change value of the selected item.
Please note that USB device type is not listed in this example. To boot this computer from a USB stick or hard drive, navigate to the topmost item, Hard Disk Boot Priority, press Enter and change the order of listed drives there (again, the USB device has to be plugged in already).

Press F10 key to save changes. You will then be asked if you want to save changes and exit (this means restart), press Y key and then press Enter.

Example four - noname laptop

This old laptop with motherboard by Insyde displays a full-screen logo with shortcut keys on bottom left. Press F2 key while this logo is displayed to access BIOS setup.

Some letters are red in the top menu, this means that you can open the menu by holding down Alt key and pressing the red letter key - for example, you can open Boot menu by pressing Alt+B.

Open Boot menu, use arrow down key to select Boot Sequence and then press Enter key:

Press Tab key twice to activate device type selection. Move to a device type with arrow keys, then use PageUp and PageDown keys to move it up or down in the list. Press Enter confirm changes.
As there is no entry for USB devices, you must choose HDD Sequence (Alt+H) from Boot menu and use the same keys to change boot sequence there.

Open Exit menu by pressing Alt+X on your keyboard, choose Save and Exit with down arrow key and press Enter twice to save new configuration and restart your computer.

I hope these two examples gave you enough information to change boot order on your computer.