Failed update from 8.1 to 10

I bought a dell i7 with windows 8.1 which was upgraded to W10 in store. This was fine until the anniversary update caused pc (laptop) to hang and would not restart. I reinstalled the 8.1 with disc and then used Windows 10 update assistant to attempt a re-upgrade. preparation took more than 12 hours and then I was asked for a key or if previously installed MS would search the key and proceed. Since then I can do nothing with my laptop. All I get is a static screen with Dell logo. When I reinserted the original disc it would not repair and returned to the same screen. I cannot even get the dvd drive to open. Any help will be appreciated
The only thing I can do is turn power on and off - not even the cursor appears