I searched for a while through the Internet to finally find a comment with the answer: in a multi-screen configuration, if you want to turn the screens off without Windows disabling them, you just have to disable PCI-Express energy savings.
- Control panel
- Energy saving things
- Energy schema window->Edit scheme settings (a blue link on my machine) Next to the actual settings mode
- You can see a window where you can set up the monitor automatic turn on and off. Here is a link Special energy settings thing…
- A new window comes up, where you can see all the devices, such as USB, HDD and so on.
- Find the PCI Express device, and turn the energy savings off
Source: Technet Microsoft