bro i also had the same problem but i tried it by my own method
when you turn on press F12 as the moment you see dell symbol
Then i dont rember the exact but select last option below bios setup
then after reaching there ther will be futhur two option you try both one at a time while doing this you will see dell warning to change that setting but you do that .It worked for i too search the whole internet but didnt found the solution anywhere but this my method worked for me hope it will work for you