An Alienware computer has a Basic Input Output System (BIOS) setup menu that can be accessed when you turn on the computer. This only requires that you press a certain key at bootup. Once inside the BIOS, you should take caution to not make any changes you are not comfortable making, since they could affect the performance of your computer in a negative way.
Start your computer and wait for the Alienware splash screen to appear.
Quickly tap the "F2" button to order the computer to boot in the BIOS menu.
Press the "Esc" key to exit the BIOS menu and continue the normal boot sequence.