[Bob256]

To get the ASUS X55U to boot first from the DVD drive do the following:

Press “ESC” or “F2” to enter the BIOS setup
Under the “Boot” tab, enable “Launch CSM”
Under the “Security” tab, disable “Secure Boot Control”
Save the changes and exit
Press “ESC” or “F2” to enter the BIOS setup again
Under the “Boot” tab, the DVD drive and available flash drives will appear. Set the DVD drive as the first boot option.
Save the changes and exit

В целом в момент загрузки или “ESC” или "F8" или "F2" бывает "F12" для входа в boot menu