Dell Alienware 15 (Early 2015) - Manual (Page 147)

2 Use the arrow keys to highlight the Boot menu option and press Enter to
access the menu.
NOTE: Note your current boot sequence in case you want to restore
it.
3 Navigate to Set Boot Priority to configure the boot priority.
4 Use the arrow keys to highlight the boot priority and press Enter to display
the different devices.
5 Select the device and press Enter to set the boot priority.
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