Dell Alienware 13 (Late 2014) - Manual (Page 117)

4 On the Boot Options, select the device you want to boot from and press
Enter.
For example, if you are booting to a USB hard drive, highlight
USB Hard
Disk and press Enter.
Changing Boot Sequence for Future Boots
1 Enter system setup.
See "
Entering System Setup ".
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 Double-click or use the arrow keys to highlight the boot priority and press
Enter to display the different devices.
5 Select the device and press Enter or double-click to set the boot priority.
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