You may need to change the boot order to get it to allow you to boot up through USB.
NOTE: Before you set boot priority for a USB device, plug the device into a USB port.
To specify the boot sequence (as in what order the drives load in)...
1. Turn on the computer and then, during the initial startup (first or second screen), press ESC, F1,
F2, F8 or F10 (depending on which your device uses to get to BIOS).
2. Now enter BIOS setup. (It can mistakenly be called Aptio Setup sometimes because that is the title
in the screen, but this is BIOS).
3. Use the arrow keys and select the BOOT tab. You should now see "System devices" shown in order of
priority (which starts up when).
4a. To give a cd or dvd priority in the sequence over the hard drive/hdd/sdd, move it to the first
position in the list.
4b. To give a USB priority in the sequence over the hard drive/hdd/sdd, do the following...
A. First move the hard drive/hdd/sdd to the top of the boot sequence list.
B. Open the hard drive/hdd/sdd device in the list and it should display all hard drives.
C. Now move the USB device to the top of the list of hard drives.
5. Now save and exit the BIOS setup utility.
6. The computer should now restart with the changed settings.
Now if you want to set the boot priority using a device selection menu...
1. When the computer first starts to boot up, just after the manufacturer's logo screen, press F12
(probably a few times, in quick succession).
2. The device selection menu should show up now.
3. Use the up and down arrows keys to select CD, DVD or USB Flash Drive.
4. To set it to boot from the selected device, press ENTER.