I Had the same problem and nothing worked I tried them all the reset hard reset and I would get a spinning gears or flashing red battery icon than id charged it for 4hrs and more spinning gears. I even had the bricked phone Icon with a lighting bolt and gear and it fix it no problem.
Here is what I did
#1. On your PC or TabletGo to this web site http://www.wpcentral.com/suffering-spinning-cogs-issue-nokia-windows-phone-fix
#2. Download and install on to your PC or windows Tablet the Nokia Software
#3. Using your charging cord plug your phone into computer
#4 Run the program and when it starts searching for the a connected phone or says it cant find a device do a hard reset which is Power+Vol Down+Camera button when phone vibrates Only release Power Button and Nokia screen will come up and than turn off release all buttons and the program should recognize your phone and let you know there is a Firmware update click Yes to update. Leave your phone pluged in and after a few minutes you will see a Blue Nokia Screen on your phone than your phone will restart again and FINALLY BOOT BACK UP!!! its nothing but smiles from there.