This is a FAQ that I get.. Why won't the image on my laptop show on a TV or projector?
When trying to "toggle" between a TV or projector and a laptop (through the FN-F7--or other keys depending on model) You can NOT have a video application playing on your laptop at that time!
So for example, you have your laptop up, and you start playing a video through windows media player or VLC, etc. and then you try to toggle your screens so that you can see it on the TV or a projector...It will keep saying "no input" no matter how many times you hit the FN-F7 keys. So what you should do ? Close out of any video program you are playing, try toggling again by using the FN-F7 keys, and it should then show on the TV. Then open up the video again.
Here's more on connecting laptops to TV's:
Another common problem that people forget about with laptops and showing videos is that on many laptops there is volume control for the laptop just above the function keys. Sometimes, You have to hit the UP volume there (as well as check the volume control in your system tray) in order for sound to come out. It's also good to make sure your audio cable going from the TV is plugged into the (generally green) audio out connection on the side of your laptop.