How to turn off ONE monitor in a multi-monitor setup?

I have a Lenovo W700 laptop to which I have connected one external monitor. So, I'm using the laptop screen and the external monitor. At times, I'd like to dim/turn off the laptop screen, while leaving the external monitor on. However, everything I've found affects both screens and doesn't have the option of dimming just the laptop screen.

Closing the laptop turns off the screen, but it shoves any/all open windows over to the external monitor, messing things up. I just want to dim to black, leaving the laptop screen windows as-is.

Any ideas on how to accomplish this??

 

one of your function keys should be able to toggle the screens Fn+F7 ?

it should toggle something like [laptop only <> both <> external only]

 

You may need a multi-monitor program such as UltraMon but I'm not sure that does what you're asking for either.

 

Don't you have the option to adjust the brightness on the laptop's screen with the fn keys. This works on my Asus, i can dim the laptop's lcd with the fn+F keys while keeping my main monitor at the same brightness level.

 

Already tried this. It does similar to just closing the lid. Turning off/on the laptop screen ends up moving windows around to/from laptop and the external monitor.

I would like at least for windows on external monitor to stay put when I turn the laptop screen back on. Using Fn+F7 moves stuff from the external monitor to the laptop screen.