Dell Alienware 15 (Early 2015) - Manual (Page 146)

Floppy (Diskette Drive) — The computer attempts to boot from the floppy
disk drive. If no operating system is on the drive, the computer generates an
error message.
Hard Drive — The computer attempts to boot from the primary hard drive. If
no operating system is on the drive, the computer generates an error message.
CD/DVD/CD-RW Drive — The computer attempts to boot from the optical
drive. If no disc is in the drive, or if the disc is not bootable, the computer
generates an error message.
USB Storage Device — Insert the memory device into a USB connector and
restart the computer. When
F12 Boot Options appear in the lower-right
corner of the screen, press F12. The BIOS detects the device and adds the USB
flash option to the boot menu.
NOTE: To boot to a USB device, the device must be bootable. To ensure
that your device is bootable, check the device documentation.
Network — The computer attempts to boot from the network. If no operating
system is found on the network, the computer generates an error message.
Changing boot sequence for the current boot
1 If you are booting from a USB device, connect the USB device to a USB port.
2 Turn on (or restart) your computer.
3 When F2 Setup, F12 Boot Options appear in the lower-right corner of
the screen, press F12.
NOTE: If you wait too long and the operating system logo appears,
continue to wait until you see the Microsoft Windows desktop. Then,
shut down your computer and try again.
The Boot Options appears, listing all available boot devices.
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 BIOS setup program.
See "
Entering BIOS setup program ".
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