system recovery problem

I have a situation like you but with my Sony UX380N.
I also have an external DVD ROM drive but my computer did not recognize the drive through USB cable. I contacted Sony Tech support; they told me to use Fs keys but my did not work. May be it will work for you.
To reset the BIOS hit Fn+F2
To reset/system recovery hit Fn+F10
if it is working i will let me know so I will congratulate you.
Also if you find out how it work for your computer please let me know how.
I have tried everything but it did not work.
Good luck