dual boot - Install alongside Windows 10 missing

I got a new Dell xps15 with Win 10 and I am trying to install Ubuntu 16 on dual boot.

I am following this guide:http://www.everydaylinuxuser.com/2015/11/how-to-install-ubuntu-linux-alongside.html

This is what I did:

1. Download Ubuntu iso and create the usb pen boot drive


2. Shrink the main C drive, now I have 229 Gb not allocated


3. Restart and boot from usb.

The problem is that when I arrive to the "Installation type" window, there is not the option "Install along side window" but only this:

/dev/sda

enter image description here

and if I click install an error occurs

What can I do?