Solution is simply, sell your Laptop and buy different then Dell.
WHY????
In 2013 I bought Inspiron 7520 and I got same problem like you. I checked forum, everybody same problem. I call to Dell support service (they are in India) and spoke with them more then 40 hours together.
They send me same new laptop, problem was same.
Another problem was with Steam and Origin software for games. When I install and start them my Dell got crash. They recommend me to uninstall this software and never use it any more.... OK but I bought this laptop because I wanted play games. Call service don't care.
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I found only one solution how to fix this. You need DVD with Windows 8 from Dell support and you have to completely re-install your Laptop. Make full format your HDD and install new Win. You will lost all pre-install software for your Inspiron, but stable win with switchable GPU.
Sorry I don't remember steps. It was two years ago.
After It's gonna be almost OK. You will have your GPU and you can play games but you cannot install official AMD drivers because it will get crash, you can install only Dell AMD driver for your laptop. Which my driver is old since 2013 and they didn't change it for new.
Now is 2015 and I have problems with new games, graphic software and movies becouse Dell drivers are old. It's too much problems for too much money.
I'm gonna buy ASUS GH551JW, which is totally OK. Never buy mobile AMD video card, similar problems with games.